draft-ietf-pint-protocol-03.txt   rfc2848.txt 
INTERNET-DRAFT Scott Petrack,
Internet Engineering Task Force MetaTel
PINT Working Group Lawrence Conroy,
Issued: 18 February 2000 Siemens Roke Manor Research
Expires: 18 August 2000
The PINT Service Protocol: Network Working Group S. Petrack
Extensions to SIP and SDP for IP Access to Telephone Call Services Request for Comments: 2848 MetaTel
Category: Standards Track L. Conroy
Siemens Roke Manor Research
June 2000
<draft-ietf-pint-protocol-03.txt> The PINT Service Protocol:
Extensions to SIP and SDP for IP Access to Telephone Call Services
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (c) The Internet Society (1999). All rights reserved. Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract Abstract
This document contains the specification of the PINT Service Protocol This document contains the specification of the PINT Service Protocol
1.0, which defines a protocol for invoking certain telephone services 1.0, which defines a protocol for invoking certain telephone services
from an IP network. These services include placing basic calls, sending from an IP network. These services include placing basic calls,
and receiving faxes, and receiving content over the telephone. The sending and receiving faxes, and receiving content over the
protocol is specified as a set of enhancements and additions to the SIP telephone. The protocol is specified as a set of enhancements and
2.0 and SDP protocols. additions to the SIP 2.0 and SDP protocols.
This document is intended for the PSTN-Internet Interworking (PINT)
working group of the Internet Engineering Task Force. Comments are
solicited and should be addressed to the working group's mailing list at
pint@lists.research.bell-labs.com and/or the authors.
Petrack & Conroy [Page 1]
Contents
1. Introduction .................................................... 4
1.1 Glossary ....................................................... 6
2. PINT Milestone Services ......................................... 6
2.1 Request to Call ............................................ 6
2.2 Request to Fax ............................................. 6
2.3 Request to Hear Content .................................... 7
2.4 Relation between PINT milestone services and traditional
telephone services .......................................... 7
3. PINT Functional and Protocol Architecture ........................ 7
3.1. PINT Functional Architecture ............................... 7
3.2. PINT Protocol Architecture ................................. 8
3.2.1. SDP operation in PINT ................................ 9
3.2.2. SIP Operation in PINT ............................... 10
3.3. REQUIRED and OPTIONAL elements for PINT compliance ........ 10
3.4. PINT Extensions to SDP 2.0 ................................ 11
3.4.1. Network Type "TN" and Address Type "RFC2543" ........ 11
3.4.2. Support for Data Objects within PINT ................ 12
3.4.2.1. Use of fmtp attributes in PINT requests ....... 14
3.4.2.2. Support for Remote Data Object References
in PINT .................................... 15
3.4.2.3. Support for GSTN-based Data Objects in PINT.... 15
3.4.2.4. Session Description support for included Data
Objects .................................... 17
3.4.3. Attribute Tags to pass information into the Telephone
Network .................................... 17
3.4.3.1. The phone-context attribute ................... 18
3.4.3.2. Presentation Restriction attribute ............ 20
3.4.3.3. ITU-T CalledPartyAddress attributes parameters 21
3.4.4. The "require" attribute ............................. 22
3.5. PINT Extensions to SIP 2.0 ................................ 23
3.5.1. Multi-part MIME (sending data along with SIP request) 23
3.5.2. Warning header ...................................... 24
3.5.3. Mechanism to register interest in the disposition of
a PINT service, and to receive indications on that
disposition ........................................ 24
3.5.3.1. Opening a monitoring session with a SUBSCRIBE
request .................................... 25
3.5.3.2. Sending Status Indications with a NOTIFY
request .................................... 26
3.5.3.3. Closing a monitoring session with an UNSUBSCRIBE
request ....................................... 27
3.5.3.4. Timing of SUBSCRIBE requests .................. 28
3.5.4. The "Require:" header for PINT ...................... 28
3.5.5. PINT URLs within PINT requests ...................... 29
3.5.5.1. PINT URLS within Request-URIs ................. 29
3.5.6. Telephony Network Parameters within PINT URLs ....... 30
3.5.7. REGISTER requests within PINT ....................... 30
3.5.8. BYE Requests in PINT ................................ 31
Petrack & Conroy [Page 2]
4. Examples of PINT Requests and Responses ......................... 32
4.1. A request to a call center from an anonymous user to receive
a phone call ........................................... 32
4.2. A request from a non anonymous customer (John Jones) to
receive a phone call from a particular sales agent
(Mary James) ........................................... 33
4.3. A request to get a fax back ............................... 34
4.4. A request to have information read out over the phone ..... 34
4.5. A request to send an included text page to a friend's pager 35
4.6. A request to send an image as a fax to phone number
+972-9-956-1867 ........................................ 35
4.7. A request to read out over the phone two pieces of content
in sequence ............................................ 36
4.8. Request for the prices for ISDN to be sent to my fax
machine ................................................ 36
4.9. Request for a callback .................................... 37
4.10.Sending a set of information in response to an enquiry .... 37
4.11.Sportsline "headlines" message sent to your phone/fax/pager 38
4.12.Automatically giving someone a fax copy of your phone bill 39
5. Security Considerations ......................................... 40
5.1. Basic Principles for PINT Use ............................ 40
5.1.1. Responsibility for service requests ................ 40
5.1.2. Authority to make requests ......................... 41
5.1.3. Privacy ............................................ 41
5.1.4. Privacy Implications of SUBSCRIBE/NOTIFY ........... 42
5.2. Registration Procedures .................................. 42
5.3. Security mechanisms and implications on PINT service ..... 43
5.4. Summary of Security Implications ......................... 45
6. Deployment considerations and the Relationship PINT to I.N. Table of Contents
(Informative) ................................................... 47
6.1. Web Front End to PINT Infrastructure ...................... 47
6.2. Redirects to Multiple Gateways ............................ 47
6.3. Competing PINT Gateways REGISTERing to offer the same
service ................................................ 48
6.4. Limitations on Available Information and Request Timing for
SUBSCRIBE .............................................. 49
6.5. Parameters needed for invoking traditional GSTN Services
within PINT............................................. 51
6.5.1. Service Identifier .................................. 51
6.5.2. A and B parties ..................................... 51
6.5.3. Other Service Parameters ............................ 51
6.5.4. Service Parameter Summary ........................... 52
6.6. Parameter Mapping to PINT Extensions....................... 53
7. Open Issues and Draft State ..................................... 55 1. Introduction ................................................. 4
7.1. Open Issues ............................................... 55 1.1 Glossary .................................................... 6
7.2. Draft State ............................................... 55 2. PINT Milestone Services ...................................... 6
8. References ...................................................... 55 2.1 Request to Call ............................................. 7
9. Acknowledgements ................................................ 56 2.2 Request to Fax Content ...................................... 7
Appendix A: Collected ABNF for PINT Extensions ..................... 57 2.3 Request to Speak/Send/Play Content .......................... 7
Appendix B: IANA Considerations .................................... 61 2.4 Relation between PINT milestone services and traditional
Appendix C: Authors' Addresses ..................................... 63 telephone services .......................................... 7
3. PINT Functional and Protocol Architecture .................... 8
3.1. PINT Functional Architecture ............................... 8
3.2. PINT Protocol Architecture ................................. 9
3.2.1. SDP operation in PINT .................................... 10
3.2.2. SIP Operation in PINT .................................... 11
3.3. REQUIRED and OPTIONAL elements for PINT compliance ......... 11
3.4. PINT Extensions to SDP 2.0 ................................. 12
3.4.1. Network Type "TN" and Address Type "RFC2543" ............. 12
3.4.2. Support for Data Objects within PINT ..................... 13
3.4.2.1. Use of fmtp attributes in PINT requests ................ 15
3.4.2.2. Support for Remote Data Object References in PINT ...... 16
3.4.2.3. Support for GSTN-based Data Objects in PINT ............ 17
3.4.2.4. Session Description support for included Data Objects .. 18
3.4.3. Attribute Tags to pass information into the Telephone
Network .................................................. 19
3.4.3.1. The phone-context attribute ............................ 20
3.4.3.2. Presentation Restriction attribute ..................... 22
3.4.3.3. ITU-T CalledPartyAddress attributes parameters ......... 23
3.4.4. The "require" attribute .................................. 24
3.5. PINT Extensions to SIP 2.0 ................................. 25
3.5.1. Multi-part MIME (sending data along with SIP request) .... 25
3.5.2. Warning header ........................................... 27
3.5.3. Mechanism to register interest in the disposition of a PINT
service, and to receive indications on that disposition .. 27
3.5.3.1. Opening a monitoring session with a SUBSCRIBE request .. 28
3.5.3.2. Sending Status Indications with a NOTIFY request ....... 30
3.5.3.3. Closing a monitoring session with an UNSUBSCRIBE request 30
3.5.3.4. Timing of SUBSCRIBE requests ........................... 31
3.5.4. The "Require:" header for PINT ........................... 32
3.5.5. PINT URLs within PINT requests ........................... 32
3.5.5.1. PINT URLS within Request-URIs .......................... 33
3.5.6. Telephony Network Parameters within PINT URLs ............ 33
3.5.7. REGISTER requests within PINT ............................ 34
3.5.8. BYE Requests in PINT ..................................... 35
4. Examples of PINT Requests and Responses ...................... 37
4.1. A request to a call center from an anonymous user to receive
a phone call ............................................... 37
4.2. A request from a non anonymous customer (John Jones) to
receive a phone call from a particular sales agent
(Mary James) ............................................... 37
4.3. A request to get a fax back ................................ 38
4.4. A request to have information read out over the phone ...... 39
4.5. A request to send an included text page to a friend's pager. 39
4.6. A request to send an image as a fax to phone number
+972-9-956-1867 ............................................ 40
4.7. A request to read out over the phone two pieces of content
in sequence ................................................ 41
4.8. Request for the prices for ISDN to be sent to my fax
machine .................................................... 42
4.9. Request for a callback ..................................... 42
4.10.Sending a set of information in response to an enquiry ..... 43
4.11.Sportsline "headlines" message sent to your phone/fax/pager 44
4.12.Automatically giving someone a fax copy of your phone bill . 45
5. Security Considerations ...................................... 46
5.1. Basic Principles for PINT Use ............................. 46
5.1.1. Responsibility for service requests ..................... 46
5.1.2. Authority to make requests .............................. 47
5.1.3. Privacy ................................................. 47
5.1.4. Privacy Implications of SUBSCRIBE/NOTIFY ................ 48
5.2. Registration Procedures ................................... 49
5.3. Security mechanisms and implications on PINT service ...... 50
5.4. Summary of Security Implications .......................... 52
6. Deployment considerations and the Relationship PINT to I.N.
(Informative) ................................................ 54
6.1. Web Front End to PINT Infrastructure ....................... 54
6.2. Redirects to Multiple Gateways ............................. 54
6.3. Competing PINT Gateways REGISTERing to offer the same
service .................................................... 55
6.4. Limitations on Available Information and Request Timing for
SUBSCRIBE .................................................. 56
6.5. Parameters needed for invoking traditional GSTN Services
within PINT................................................. 58
6.5.1. Service Identifier ....................................... 58
6.5.2. A and B parties .......................................... 58
6.5.3. Other Service Parameters ................................. 59
6.5.4. Service Parameter Summary ................................ 59
6.6. Parameter Mapping to PINT Extensions........................ 60
7. References ................................................... 62
8. Acknowledgements ............................................. 64
Appendix A: Collected ABNF for PINT Extensions .................. 65
Appendix B: IANA Considerations ................................. 69
Authors' Addresses .............................................. 72
Full Copyright Statement ........................................ 73
Petrack & Conroy [Page 3]
1. Introduction 1. Introduction
The desire to invoke certain telephone call services from the Internet The desire to invoke certain telephone call services from the
has been identified by many different groups (users, public and private Internet has been identified by many different groups (users, public
network operators, call center service providers, equipment vendors, see and private network operators, call center service providers,
[7]). The generic scenario is as follows (when the invocation is equipment vendors, see [7]). The generic scenario is as follows (when
successful): the invocation is successful):
1. an IP host sends a request to a server on an IP network; 1. an IP host sends a request to a server on an IP network;
2. the server relays the request into a telephone network; 2. the server relays the request into a telephone network;
3. the telephone network performs the requested call service. 3. the telephone network performs the requested call service.
As examples, consider a user who wishes to have a callback placed to As examples, consider a user who wishes to have a callback placed to
his/her telephone. It may be that a customer wants someone in the his/her telephone. It may be that a customer wants someone in the
support department of some business to call them back. Similarly, a user support department of some business to call them back. Similarly, a
may want to hear some announcement of a weather warning sent from a user may want to hear some announcement of a weather warning sent
remote automatic weather service in the event of a storm. from a remote automatic weather service in the event of a storm.
We use the term "PSTN/Internet Interworking (PINT) Service" to denote We use the term "PSTN/Internet Interworking (PINT) Service" to denote
such a complete transaction, starting with the sending of a request from such a complete transaction, starting with the sending of a request
an IP client and including the telephone call itself. PINT services are from an IP client and including the telephone call itself. PINT
distinguished by the fact that they always involve two separate services are distinguished by the fact that they always involve two
networks: separate networks:
an IP network to request the placement of a call, and the Global
Switched Telephone Network (GSTN) to execute the actual call. It is
understood that Intelligent Network systems, private PBXs, cellular
phone networks, and the ISDN can all be used to deliver PINT services.
Also, the request for service might come from within a private IP
network that is disconnected from the whole Internet.
The requirements for the PINT protocol were deliberately restricted to an IP network to request the placement of a call, and the Global
providing the ability to invoke a small number of fixed telephone call Switched Telephone Network (GSTN) to execute the actual call. It
services. These "Milestone PINT services" are specified in section 2. is understood that Intelligent Network systems, private PBXs,
Great care has been taken, however, to develop a protocol that is cellular phone networks, and the ISDN can all be used to deliver
aligned with other Internet protocols where possible, so that future PINT services. Also, the request for service might come from
extensions to PINT could develop along with Internet conferencing. within a private IP network that is disconnected from the whole
Internet.
Within the Internet conference architecture, establishing media calls is The requirements for the PINT protocol were deliberately restricted
done via a combination of protocols. SIP [1] is used to establish the to providing the ability to invoke a small number of fixed telephone
association between the participants within the call (this association call services. These "Milestone PINT services" are specified in
between participants within the call is called a "session"), and SDP [2] section 2. Great care has been taken, however, to develop a protocol
is used to describe the media to be exchanged within the session. The that is aligned with other Internet protocols where possible, so that
PINT protocol uses these two protocols together, providing some future extensions to PINT could develop along with Internet
extensions and enhancements to enable SIP clients and servers to become conferencing.
PINT clients and servers.
A PINT user who wishes to invoke a service within the telephone network Within the Internet conference architecture, establishing media calls
uses SIP to invite a remote PINT server into a session. The invitation is done via a combination of protocols. SIP [1] is used to establish
contains an SDP description of the media session that the user would the association between the participants within the call (this
like to take place. This might be a "sending a fax session" or a association between participants within the call is called a
"telephone call session", for example. In a PINT service execution "session"), and SDP [2] is used to describe the media to be exchanged
session the media is transported over the phone system, while in a SIP within the session. The PINT protocol uses these two protocols
session the media is normally transported over an internet. together, providing some extensions and enhancements to enable SIP
clients and servers to become PINT clients and servers.
Petrack & Conroy [Page 4] A PINT user who wishes to invoke a service within the telephone
When used to invoke a PINT service, SIP establishes an association network uses SIP to invite a remote PINT server into a session. The
between a requesting PINT client and the PINT server that is responsible invitation contains an SDP description of the media session that the
for invoking the service within the telephone network. These two user would like to take place. This might be a "sending a fax
entities are not the same entities as the telephone network entities session" or a "telephone call session", for example. In a PINT
involved in the telephone network service. The SIP messages carry within service execution session the media is transported over the phone
their SDP payloads a description of the telephone network media session. system, while in a SIP session the media is normally transported over
an internet.
Note that the fact that a PINT server accepts an invitation and a When used to invoke a PINT service, SIP establishes an association
session is established is no guarantee that the media will be between a requesting PINT client and the PINT server that is
successfully transported. (This is analogous to the fact that if a SIP responsible for invoking the service within the telephone network.
invitation is accepted successfully, this is no guarantee against a These two entities are not the same entities as the telephone network
subsequent failure of audio hardware). entities involved in the telephone network service. The SIP messages
carry within their SDP payloads a description of the telephone
network media session.
The particular requirements of PINT users lead to some new messages. Note that the fact that a PINT server accepts an invitation and a
When a PINT server agrees to send a fax to telephone B, it may be that session is established is no guarantee that the media will be
the fax transmission fails after part of the fax is sent. Therefore, the successfully transported. (This is analogous to the fact that if a
PINT client may wish to receive information about the status of the SIP invitation is accepted successfully, this is no guarantee against
actual telephone call session that was invoked as a result of the a subsequent failure of audio hardware).
established PINT session. Three new requests, SUBSCRIBE, UNSIUBSCRIBE,
and NOTIFY, are added here to vanilla SIP to allow this.
The enhancements and additions specified here are not intended to alter The particular requirements of PINT users lead to some new messages.
the behaviour of baseline SIP or SDP in any way. The purpose of PINT When a PINT server agrees to send a fax to telephone B, it may be
extensions is to extend the usual SIP/SDP services to the telephone that the fax transmission fails after part of the fax is sent.
world. Apart from integrating well into existing protocols and Therefore, the PINT client may wish to receive information about the
architectures, and the advantages of reuse, this means that the protocol status of the actual telephone call session that was invoked as a
specified here can handle a rather wider class of call services than result of the established PINT session. Three new requests,
just the Milestone services. SUBSCRIBE, UNSUBSCRIBE, and NOTIFY, are added here to vanilla SIP to
allow this.
The rest of this document is organised as follows: Section 2 describes The enhancements and additions specified here are not intended to
the PINT Milestone services; section 3 specifies the PINT functional and alter the behaviour of baseline SIP or SDP in any way. The purpose of
protocol architecture; section 4 gives examples of the PINT 1.0 PINT extensions is to extend the usual SIP/SDP services to the
extensions of SIP and SDP; section 5 contains some security telephone world. Apart from integrating well into existing protocols
considerations for PINT. The final section contains descriptions of how and architectures, and the advantages of reuse, this means that the
the PINT protocol may be used to provide service over the GSTN. protocol specified here can handle a rather wider class of call
services than just the Milestone services.
For a summary of the extensions to SIP and SDP specified in this The rest of this document is organised as follows: Section 2
document, Section 3.2 gives an combined list, plus one each describing describes the PINT Milestone services; section 3 specifies the PINT
the extensions to SIP and SDP respectively. functional and protocol architecture; section 4 gives examples of the
PINT 1.0 extensions of SIP and SDP; section 5 contains some security
considerations for PINT. The final section contains descriptions of
how the PINT protocol may be used to provide service over the GSTN.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", For a summary of the extensions to SIP and SDP specified in this
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document, Section 3.2 gives an combined list, plus one each
document are to be interpreted as described in RFC 2119. In addition, describing the extensions to SIP and SDP respectively.
the construct "MUST .... OR ...." implies that it is an absolute
requirement of this specification to implement one of the two The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
possibilities stated (represented by dots in the above phrase). An "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
implementation MUST be able to interoperate with another implementation document are to be interpreted as described in RFC 2119. In addition,
that chooses either of the two possibilities. the construct "MUST .... OR ...." implies that it is an absolute
requirement of this specification to implement one of the two
possibilities stated (represented by dots in the above phrase). An
implementation MUST be able to interoperate with another
implementation that chooses either of the two possibilities.
Petrack & Conroy [Page 5]
1.1 Glossary 1.1 Glossary
Requestor - An Internet host from which a request for service originates
PINT Service - A service invoked within a phone system in response to a Requestor - An Internet host from which a request for service
request received from an PINT client. originates
PINT Client - An Internet host that sends requests for invocation of a PINT Service - A service invoked within a phone system in response to
PINT Service, in accordance with this document. a request received from an PINT client.
PINT Gateway - An Internet host that accepts requests for PINT Service PINT Client - An Internet host that sends requests for invocation of
and dispatches them onwards towards a telephone network. a PINT Service, in accordance with this document.
Executive System - A system that interfaces to PINT Server and to a PINT Gateway - An Internet host that accepts requests for PINT
telephone network that executes a PINT service. It need not be directly Service and dispatches them onwards towards a telephone network.
associated with the Internet, and is represented by the PINT Server in
transactions with Internet entities.
Requesting User - The initiator of a request for service. This role may Executive System - A system that interfaces to a PINT Server and to a
be distinct from that of the "party" to any telephone network call that telephone network that executes a PINT service. It need not be
results from the request. directly associated with the Internet, and is represented by the PINT
Server in transactions with Internet entities.
(Service Call) Party - A person who is involved in a telephone network Requesting User - The initiator of a request for service. This role
call that results from the execution of a PINT service request, or a may be distinct from that of the "party" to any telephone network
telephone network-based resource that is involved (such as an automatic call that results from the request.
Fax Sender or a Text-to-Speech Unit).
(Service Call) Party - A person who is involved in a telephone
network call that results from the execution of a PINT service
request, or a telephone network-based resource that is involved (such
as an automatic Fax Sender or a Text-to-Speech Unit).
2. PINT Milestone Services 2. PINT Milestone Services
The original motivation for defining this protocol was the desire to The original motivation for defining this protocol was the desire to
invoke the following three telephone network services from within an IP invoke the following three telephone network services from within an
network: IP network:
2.1 Request to Call 2.1 Request to Call
A request is sent from an IP host that causes a phone call to be made, A request is sent from an IP host that causes a phone call to be
connecting party A to some remote party B. made, connecting party A to some remote party B.
2.2 Request to Fax 2.2 Request to Fax Content
A request is sent from an IP host that causes a fax to be sent to fax A request is sent from an IP host that causes a fax to be sent to fax
machine B. The request MUST contain a pointer to the fax data (that machine B. The request MAY contain a pointer to the fax data (that
could reside in the IP network or in the Telephone Network), OR the fax could reside in the IP network or in the Telephone Network), OR the
data itself. The content of the fax MAY be text OR some other more fax data itself. The content of the fax MAY be text OR some other
general image data. The details of the fax transmission are not more general image data. The details of the fax transmission are not
accessible to the IP network, but remain entirely within the telephone accessible to the IP network, but remain entirely within the
network. telephone network.
The PINT Request to Fax service does not involve "Fax over IP": the IP Note that this service does not relate to "Fax over IP": the IP
network is only used to send the request that a certain fax be sent. Of network is only used to send the request that a certain fax be sent.
course, it is possible that the resulting telephone network fax call Of course, it is possible that the resulting telephone network fax
happens to use a real-time IP fax solution, but this is completely call happens to use a real-time IP fax solution, but this is
transparent to the PINT transaction. completely transparent to the PINT transaction.
Petrack & Conroy [Page 6] 2.3 Request to Speak/Send/Play Content
2.3 Request to Hear Content
A request is sent from an IP host that causes a phone call to be made to A request is sent from an IP host that causes a phone call to be made
user A, and for some sort of content to be spoken out. The request MUST to user A, and for some sort of content to be spoken out. The request
EITHER contain a URL pointing to the content, OR include the content MUST EITHER contain a URL pointing to the content, OR include the
itself. The content MAY be text OR some other more general application content itself. The content MAY be text OR some other more general
data. The details of the content transmission are not accessible to the application data. The details of the content transmission are not
IP network, but remain entirely within the telephone network. This accessible to the IP network, but remain entirely within the
service could equally be called "Request to have Content Spoken"; the telephone network. This service could equally be called "Request to
user's goal is to hear the content spoken to them. The mechanism by Hear Content"; the user's goal is to hear the content spoken to them.
which the request is formulated is outside the scope of this document; The mechanism by which the request is formulated is outside the scope
however, an example might be that a Web page has a button that when of this document; however, an example might be that a Web page has a
pressed causes a PINT request to be passed to the PSTN, resulting in the button that when pressed causes a PINT request to be passed to the
content of the page (or other details) being spoken to the person. PSTN, resulting in the content of the page (or other details) being
spoken to the person.
2.4 Relation between PINT milestone services and traditional telephone 2.4 Relation between PINT milestone services and traditional telephone
services services
There are many different versions and variations of each telephone call There are many different versions and variations of each telephone
service invoked by a PINT request. Consider as an example what happens call service invoked by a PINT request. Consider as an example what
when a user requests to call 1-800-2255-287 via the PINT Request-to-Call happens when a user requests to call 1-800-2255-287 via the PINT
service. Request-to-Call service.
There may be thousands of agents in the call center, and there may be There may be thousands of agents in the call center, and there may be
any number of sophisticated algorithms and pieces of equipment that are any number of sophisticated algorithms and pieces of equipment that
used to decide exactly which agent will return the call. And once this are used to decide exactly which agent will return the call. And once
choice is made, there may be many different ways to set up the call: the this choice is made, there may be many different ways to set up the
agent's phone might ring first, and only then the original user will be call: the agent's phone might ring first, and only then the original
called; or perhaps the user might be called first, and hear some user will be called; or perhaps the user might be called first, and
horrible music or pre-recorded message while the agent is located. hear some horrible music or pre-recorded message while the agent is
located.
Similarly, when a PINT request causes a fax to be sent, there are Similarly, when a PINT request causes a fax to be sent, there are
hundreds of fax protocol details to be negotiated, as well as hundreds of fax protocol details to be negotiated, as well as
transmission details within the telephone networks used. transmission details within the telephone networks used.
PINT requests do not specify too precisely the exact telephone-side PINT requests do not specify too precisely the exact telephone-side
service. Operational details of individual events within the telephone service. Operational details of individual events within the
network that executes the request are outside the scope of PINT. This telephone network that executes the request are outside the scope of
does not preclude certain high-level details of the telephone network PINT. This does not preclude certain high-level details of the
session from being expressed within a PINT request. For example, it is telephone network session from being expressed within a PINT request.
possible to use the SDP "lang" attribute to express a language For example, it is possible to use the SDP "lang" attribute to
preference for the Request-to-Hear-Content Service. If a particular express a language preference for the Request-to-Hear-Content
PINT system wishes to allow requests to contain details of the Service. If a particular PINT system wishes to allow requests to
telephone-network-side service, it uses the SDP attribute mechanism (see contain details of the telephone-network-side service, it uses the
section 3.4.2). SDP attribute mechanism (see section 3.4.2).
3. PINT Functional and Protocol Architecture 3. PINT Functional and Protocol Architecture
3.1. PINT Functional Architecture 3.1. PINT Functional Architecture
Familiarity is assumed with SIP 2.0 [1] and with SDP [2]. Familiarity is assumed with SIP 2.0 [1] and with SDP [2].
Petrack & Conroy [Page 7] PINT clients and servers are SIP clients and servers. SIP is used to
PINT clients and servers are SIP clients and servers. SIP is used to carry the request over the IP network to the correct PINT server in a
carry the request over the IP network to the correct PINT server in a secure and reliable manner, and SDP is used to describe the telephone
secure and reliable manner, and SDP is used to describe the telephone network session that is to be invoked or whose status is to be
network session that is to be invoked or whose status is to be returned. returned.
A PINT system uses SIP proxy servers and redirect servers for their A PINT system uses SIP proxy servers and redirect servers for their
usual purpose, but at some point there must be a PINT server with the usual purpose, but at some point there must be a PINT server with the
means to relay received requests into a telephone system and to receive means to relay received requests into a telephone system and to
acknowledgement of these relayed requests. A PINT server with this receive acknowledgement of these relayed requests. A PINT server with
capability is called a "PINT gateway". A PINT gateway appears to a SIP this capability is called a "PINT gateway". A PINT gateway appears to
system as a User Agent Server. Notice that a PINT gateway appears to the a SIP system as a User Agent Server. Notice that a PINT gateway
PINT infrastructure as if it represents a "user", while in fact it appears to the PINT infrastructure as if it represents a "user",
really represents an entire telephone network infrastructure that can while in fact it really represents an entire telephone network
provide a set of telephone network services. infrastructure that can provide a set of telephone network services.
So the PINT system might appear to an individual PINT client as follows: So the PINT system might appear to an individual PINT client as
follows:
/\/\/\/\/\/\/\ /\/\/\/\/\/\/\/\ /\/\/\/\/\/\/\ /\/\/\/\/\/\/\/\
___________ \ __/___ ___\_ \ ___________ \ __/___ ___\_ \
| PINT | PINT \ PINT | PINT | |Exec| Telephone / | PINT | PINT \ PINT | PINT | |Exec| Telephone /
| client |<-------------->| server |gatewy|=====|Syst| Network \ | client |<-------------->| server |gatewy|=====|Syst| Network \
|_________| protocol / cloud |______| |____| Cloud / |_________| protocol / cloud |______| |____| Cloud /
\ \ / \ \ \ / \
/\/\/\/\/\/\/\ \/\/\/\/\/\/\/\/ /\/\/\/\/\/\/\ \/\/\/\/\/\/\/\/
Figure 1: PINT Functional Architecture Figure 1: PINT Functional Architecture
The system of PINT servers is represented as a cloud to emphasise that a The system of PINT servers is represented as a cloud to emphasise
single PINT request might pass through a series of location servers, that a single PINT request might pass through a series of location
proxy servers, and redirect servers, before finally reaching the correct servers, proxy servers, and redirect servers, before finally reaching
PINT gateway that can actually process the request by passing it to the the correct PINT gateway that can actually process the request by
Telephone Network Cloud. passing it to the Telephone Network Cloud.
The PINT gateway might have a true telephone network interface, or it The PINT gateway might have a true telephone network interface, or it
might be connected via some other protocol or API to an "Executive might be connected via some other protocol or API to an "Executive
System" that is capable of invoking services within the telephone cloud. System" that is capable of invoking services within the telephone
cloud.
As an example, within an I.N. (Intelligent Network) system, the PINT As an example, within an I.N. (Intelligent Network) system, the PINT
gateway might appear to realise the Service Control Gateway Function. In gateway might appear to realise the Service Control Gateway Function.
an office environment, it might be a server adjunct to the office PBX, In an office environment, it might be a server adjunct to the office
connected to both the office LAN and the office PBX. PBX, connected to both the office LAN and the office PBX.
The Executive System that lies beyond the PINT gateway is outside the The Executive System that lies beyond the PINT gateway is outside the
scope of PINT. scope of PINT.
3.2. PINT Protocol Architecture 3.2. PINT Protocol Architecture
This section explains how SIP and SDP work in combination to convey the This section explains how SIP and SDP work in combination to convey
information necessary to invoke telephone network sessions. the information necessary to invoke telephone network sessions.
Petrack & Conroy [Page 8] The following list summarises the extension features used in PINT
The following list summarises the extension features used in PINT 1.0. 1.0. Following on from this the features are considered separately
Following on from this the features are considered separately for SDP for SDP and then for SIP:
and then for SIP:
1) Telephony URLs in SDP Contact Fields
2) Refinement of SIP/SDP Telephony URLs
* Inclusion of private dialling plans
3) Specification of Telephone Service Provider (TSP) and/or
phone-context URL-parameters
4) Data Objects as session media
4a) Protocol Transport formats to indicate the treatment of the media
within the GSTN
5) Implicit (Indirect) media streams and opaque arguments
6) In-line data objects using multipart/mime
7) Refinement/Clarification of Opaque arguments passed onwards to
Executive Systems
* Framework for Presentation Restriction Indication
* Framework for Q.763 arguments
8) An extension mechanism for SDP to specify strictures and force
failure when a recipient does NOT support the specified extensions,
using "require" headers.
9) Mandatory support for "Warning" headers to give more detailed
information on request disposition.
10) Mechanism to register interest in the disposition of a requested
service, and to receive indications on that disposition.
Both PINT and SIP rely on features of MIME[4]. The use of SIP 2.0 is 1) Telephony URLs in SDP Contact Fields
implied by PINT 1.0, and this also implies compliance with version 1.0 2) Refinement of SIP/SDP Telephony URLs
of MIME. * Inclusion of private dialling plans
3) Specification of Telephone Service Provider (TSP) and/or phone-
context URL-parameters
4) Data Objects as session media
4a) Protocol Transport formats to indicate the treatment of the media
within the GSTN
5) Implicit (Indirect) media streams and opaque arguments
6) In-line data objects using multipart/mime
7) Refinement/Clarification of Opaque arguments passed onwards to
Executive Systems
* Framework for Presentation Restriction Indication
* Framework for Q.763 arguments
8) An extension mechanism for SDP to specify strictures and force
failure when a recipient does NOT support the specified
extensions, using "require" headers.
9) Mandatory support for "Warning" headers to give more detailed
information on request disposition.
10) Mechanism to register interest in the disposition of a requested
service, and to receive indications on that disposition.
Both PINT and SIP rely on features of MIME[4]. The use of SIP 2.0 is
implied by PINT 1.0, and this also implies compliance with version
1.0 of MIME.
3.2.1. SDP operation in PINT 3.2.1. SDP operation in PINT
The SDP payload contains a description of the particular telephone The SDP payload contains a description of the particular telephone
network session that the requestor wishes to occur in the GSTN. This network session that the requestor wishes to occur in the GSTN. This
information includes such things as the telephone network address (i.e. information includes such things as the telephone network address
the "telephone number") of the terminal(s) involved in the call, an (i.e. the "telephone number") of the terminal(s) involved in the
indication of the media type to be transported (e.g. audio, text, image call, an indication of the media type to be transported (e.g. audio,
or application data), and an indication if the information is to be text, image or application data), and an indication if the
transported over the telephone network via voice, fax, or pager information is to be transported over the telephone network via
transport. An indication of the content to be sent to the remote voice, fax, or pager transport. An indication of the content to be
telephone terminal (if there is any) is also included. sent to the remote telephone terminal (if there is any) is also
included.
SDP is flexible enough to convey these parameters independently. For SDP is flexible enough to convey these parameters independently. For
example, a request to send some text via voice transport will be example, a request to send some text via voice transport will be
fulfilled by invoking some text-to-speech-over-the-phone service, and a fulfilled by invoking some text-to-speech-over-the-phone service, and
request to send text via fax will be fulfilled by invoking some a request to send text via fax will be fulfilled by invoking some
text-to-fax service. text-to-fax service.
Petrack & Conroy [Page 9] The following is a list of PINT 1.0 enhancements and additions to
The following is a list of PINT 1.0 enhancements and additions to SDP. SDP.
a. A new network type "TN" and address types "RFC2543" and "X-..." a. A new network type "TN" and address types "RFC2543" and "X-..."
(section 3.4.1) (section 3.4.1)
b. New media types "text", "image", and "application", b. New media types "text", "image", and "application", new
new protocol transport keywords "voice", "fax" and protocol transport keywords "voice", "fax" and "pager" and the
"pager" and the associated format types and attribute tags associated format types and attribute tags (section 3.4.2)
(section 3.4.2)
c. New format specific attributes for included content data c. New format specific attributes for included content data
(section 3.4.2.4) (section 3.4.2.4)
d. New attribute tags, used to pass information to the telephone d. New attribute tags, used to pass information to the telephone
network (section 3.4.3) network (section 3.4.3)
e. A new attribute tag "require", used by a client to indicate that e. A new attribute tag "require", used by a client to indicate
some attribute is required to be supported in the server that some attribute is required to be supported in the server
(section 3.4.4) (section 3.4.4)
3.2.2. SIP Operation in PINT 3.2.2. SIP Operation in PINT
SIP is used to carry the request for telephone service from the PINT SIP is used to carry the request for telephone service from the PINT
client to the PINT gateway, and may include a telephone number if needed client to the PINT gateway, and may include a telephone number if
for the particular service. The following is a complete list of PINT needed for the particular service. The following is a complete list
enhancements and additions to SIP: of PINT enhancements and additions to SIP:
f. The multipart MIME payloads (section 3.5.1) f. The multipart MIME payloads (section 3.5.1)
g. Mandatory support for "Warning:" headers (section 3.5.2) g. Mandatory support for "Warning:" headers (section 3.5.2)
h. The SUBSCRIBE and NOTIFY, and UNSUBSCRIBE requests (section 3.5.3) h. The SUBSCRIBE and NOTIFY, and UNSUBSCRIBE requests (section
i. Require: headers (section 3.5.4) 3.5.3)
j. A format for PINT URLS within a PINT request (section 3.5.5) i. Require: headers (section 3.5.4)
k. Telephone Network Parameters within PINT URLs (section 3.5.6) j. A format for PINT URLS within a PINT request (section 3.5.5)
k. Telephone Network Parameters within PINT URLs (section 3.5.6)
Section 3.5.8 contains remarks about how BYE requests are used within Section 3.5.8 contains remarks about how BYE requests are used within
PINT. This is not an extension to baseline SIP; it is included here only PINT. This is not an extension to baseline SIP; it is included here
for clarification of the semantics when used with telephone network only for clarification of the semantics when used with telephone
sessions. network sessions.
3.3. REQUIRED and OPTIONAL elements for PINT compliance 3.3. REQUIRED and OPTIONAL elements for PINT compliance
Of these, only the TN network type (with its associated RFC2543 address Of these, only the TN network type (with its associated RFC2543
type) and the "require" attribute MUST be supported by PINT 1.0 clients address type) and the "require" attribute MUST be supported by PINT
and servers. In practice, most PINT service requests will use other 1.0 clients and servers. In practice, most PINT service requests will
changes, of which references to Data Objects in requests are most likely use other changes, of which references to Data Objects in requests
to appear in PINT requests. are most likely to appear in PINT requests.
Each of the other new PINT constructs enables a different function, and Each of the other new PINT constructs enables a different function,
a client or server that wishes to enable that particular function MUST and a client or server that wishes to enable that particular function
do so by the construct specified in this document. For example, building MUST do so by the construct specified in this document. For example,
a PINT client and server that provide only the Request-to-Call telephone building a PINT client and server that provide only the Request-to-
call service, without support for the other Milestone services, is Call telephone call service, without support for the other Milestone
allowed. services, is allowed.
The "Require:" SIP header and the "require" attribute provide a The "Require:" SIP header and the "require" attribute provide a
mechanism that can be used by clients and servers to signal their need mechanism that can be used by clients and servers to signal their
and/or ability to support specific "new" PINT protocol elements. need and/or ability to support specific "new" PINT protocol elements.
It should be noted that many optional features of SIP and SDP make sense It should be noted that many optional features of SIP and SDP make
as specified in the PINT context. One example is the SDP a=lang: sense as specified in the PINT context. One example is the SDP
attribute, which can be used to describe the preferred language of the a=lang: attribute, which can be used to describe the preferred
callee. Another example is the use of the "t=" parameter to indicate language of the callee. Another example is the use of the "t="
that the time at which the PINT service is to be invoked. This is the parameter to indicate that the time at which the PINT service is to
normal use of the "t=" field. A third example is the quality attributes. be invoked. This is the normal use of the "t=" field. A third example
Any SIP or SDP option or facility is available to PINT clients and is the quality attributes. Any SIP or SDP option or facility is
servers without change. available to PINT clients and servers without change.
Conversely, support for Data Objects within Internet Conference sessions Conversely, support for Data Objects within Internet Conference
may be useful, even if the aim is not to provide a GSTN service request. sessions may be useful, even if the aim is not to provide a GSTN
In this case, the extensions covering these items may be incorporated service request. In this case, the extensions covering these items
into an otherwise "plain" SIP/SDP invitation. Likewise, support for SDP may be incorporated into an otherwise "plain" SIP/SDP invitation.
"require" may be useful, as a framework for addition of features to a Likewise, support for SDP "require" may be useful, as a framework for
"traditional" SIP/SDP infrastructure. Again, these may be convenient to addition of features to a "traditional" SIP/SDP infrastructure.
incorporate into SIP/SDP implementations that would not be used for PINT Again, these may be convenient to incorporate into SIP/SDP
service requests. Such additions are beyond the scope of this document, implementations that would not be used for PINT service requests.
however. Such additions are beyond the scope of this document, however.
3.4. PINT Extensions to SDP 3.4. PINT Extensions to SDP
PINT 1.0 adds to SDP the possibility to describe audio, fax, and pager PINT 1.0 adds to SDP the possibility to describe audio, fax, and
telephone sessions. It is deliberately designed to hide the underlying pager telephone sessions. It is deliberately designed to hide the
technical details and complexity of the telephone network. The only underlying technical details and complexity of the telephone network.
network type defined for PINT is the generic "TN" (Telephone Network). The only network type defined for PINT is the generic "TN" (Telephone
More precise tags such as "ISDN", "GSM", are not defined. Similarly, the Network). More precise tags such as "ISDN", "GSM", are not defined.
transport protocols are designated simply as "fax", "voice", and Similarly, the transport protocols are designated simply as "fax",
"pager"; there are no more specific identifiers for the various "voice", and "pager"; there are no more specific identifiers for the
telephone network voice, fax, or pager protocols. Similarly, the data to various telephone network voice, fax, or pager protocols. Similarly,
be transported are identified only by a MIME content type, such as the data to be transported are identified only by a MIME content
"text" data, "image" data, or some more general "application" data. An type, such as "text" data, "image" data, or some more general
important example of transporting "application" data is the milestone "application" data. An important example of transporting
service "Voice Access to Web Content". In this case the data to be "application" data is the milestone service "Voice Access to Web
transported are pointed to by a URI, the data content type is Content". In this case the data to be transported are pointed to by a
application/URI, and the transport protocol would be "voice". Some sort URI, the data content type is application/URI, and the transport
of speech-synthesis facility, speaking out to a Phone, will have to be protocol would be "voice". Some sort of speech-synthesis facility,
invoked to perform this service. speaking out to a Phone, will have to be invoked to perform this
service.
This section gives details of the new SDP keywords. This section gives details of the new SDP keywords.
3.4.1. Network Type "TN" and Address Type "RFC2543" 3.4.1. Network Type "TN" and Address Type "RFC2543"
The TN ("Telephone Network") network type is used to indicate that the The TN ("Telephone Network") network type is used to indicate that
terminal is connected to a telephone network. the terminal is connected to a telephone network.
The address types allowed for network type TN are "RFC2543" and private The address types allowed for network type TN are "RFC2543" and
address types, which MUST begin with an "X-". private address types, which MUST begin with an "X-".
Address type RFC2543 is followed by a string conforming to a subset of Address type RFC2543 is followed by a string conforming to a subset
the "telephone-subscriber" BNF specified in figure 4 of SIP [1]). of the "telephone-subscriber" BNF specified in figure 4 of SIP [1]).
Note that this BNF is NOT identical to the BNF that defines the Note that this BNF is NOT identical to the BNF that defines the
"phone-number" within the "p=" field of SDP. "phone-number" within the "p=" field of SDP.
Examples: Examples:
c= TN RFC2543 +1-201-406-4090 c= TN RFC2543 +1-201-406-4090
c= TN RFC2543 12014064090 c= TN RFC2543 12014064090
A telephone-subscriber string is of one of two types: A telephone-subscriber string is of one of two types: global-phone-
global-phone-number or number or local-phone-number. These are distinguished by preceeding
local-phone-number. a global-phone-number with a "plus" sign ("+"). A global-phone-number
These are distinguished by preceeding a global-phone-number with a is by default to be interpreted as an internationally significant
"plus" sign ("+"). A global-phone-number is by default to be interpreted E.164 Number Plan Address, as defined by [6], whilst a local-phone-
as an internationally significant E.164 Number Plan Address, as defined number is a number specified in the default dialling plan within the
by [6], whilst a local-phone-number is a number specified in the default context of the recipient PINT Gateway.
dialling plan within the context of the recipient PINT Gateway.
An implementation MAY use private addressing types, which can be useful An implementation MAY use private addressing types, which can be
within a local domain. These address types MUST begin with an "X-", and useful within a local domain. These address types MUST begin with an
SHOULD contain a domain name after the X-, e.g. "X-mytype.mydomain.com". "X-", and SHOULD contain a domain name after the X-, e.g. "X-
An example of such a connection line is as follows: mytype.mydomain.com". An example of such a connection line is as
follows:
c= TN X-mytype.mydomain.com A*8-HELEN c= TN X-mytype.mydomain.com A*8-HELEN
where "X-mytype.mydomain.com" identifies this private address type, and where "X-mytype.mydomain.com" identifies this private address type,
"A*8-HELEN" is the number in this format. Such a format is defined as an and "A*8-HELEN" is the number in this format. Such a format is
"OtherAddr" in the ABNF of Appendix A. Note that most dialable telephone defined as an "OtherAddr" in the ABNF of Appendix A. Note that most
numbers are expressable as local-phone-numbers within address RFC2543; dialable telephone numbers are expressable as local-phone-numbers
new address types SHOULD only be used for formats which cannot be so within address RFC2543; new address types SHOULD only be used for
written. formats which cannot be so written.
3.4.2. Support for Data Objects within PINT 3.4.2. Support for Data Objects within PINT
One significant change over traditional SIP/SDP Internet Conference One significant change over traditional SIP/SDP Internet Conference
sessions with PINT is that a PINT service request may refer to a Data sessions with PINT is that a PINT service request may refer to a Data
Object to be used as source information in that request. For example, a Object to be used as source information in that request. For example,
PINT service request may specify a document to be processed as part of a a PINT service request may specify a document to be processed as part
GSTN service by which a Fax is sent. Similarly, a GSTN service may be of a GSTN service by which a Fax is sent. Similarly, a GSTN service
take a Web page and result in a vocoder processing that page and may be take a Web page and result in a vocoder processing that page
speaking the contents over a telephone. and speaking the contents over a telephone.
The SDP specification does not have explicit support for reference to or The SDP specification does not have explicit support for reference to
carriage of Data Objects within requests. In order to use SDP for PINT, or carriage of Data Objects within requests. In order to use SDP for
there is a need to describe such media sessions as "a telephone call to PINT, there is a need to describe such media sessions as "a telephone
a certain number during which such-and-such an image is sent as a fax". call to a certain number during which such-and-such an image is sent
as a fax".
To support this, two extensions to the session description format are To support this, two extensions to the session description format are
specified. These are some new allowed values for the Media Field, and a specified. These are some new allowed values for the Media Field, and
description of the "fmtp" parameter when used with the Media Field a description of the "fmtp" parameter when used with the Media Field
values (within the context of the Contact Field Network type "TN"). values (within the context of the Contact Field Network type "TN").
An addition is also made to the SIP message format to allow the An addition is also made to the SIP message format to allow the
inclusion of data objects as sub-parts within the request message inclusion of data objects as sub-parts within the request message
itself. The original SDP syntax (from [2]) for media-field is given as: itself. The original SDP syntax (from [2]) for media-field is given
media-field = "m=" media space port ["/" integer] as:
space proto 1*(space fmt) CRLF
When used within PINT requests, the definition of the sub-fields is
expanded slightly. The Media sub-field definition is relaxed to accept
all of the discrete "top-level" media types defined in [4]. In the
milestone services the discrete type "video" is not used, and the extra
types "data" and "control" are likewise not needed. The use of these
types is not precluded, but the behaviour expected of a PINT Gateway
receiving a request including such a type is not defined here.
The Port sub-field has no meaning in PINT requests as the destination media-field = "m=" media space port ["/" integer]
terminals are specified using "TN" addressing, so the value of the port space proto 1*(space fmt) CRLF
sub-field in PINT requests is normally set to "1". A value of "0" may be
used as in SDP to indicate that the terminal is not receiving media.
This is useful to indicate that a telephone terminal has gone "on hold"
temporarily. Likewise, the optional integer sub-field is not used in
PINT.
As mentioned in [2], the Transport Protocol sub-field is specific to the When used within PINT requests, the definition of the sub-fields is
associated Address Type. In the case that the Address Type in the expanded slightly. The Media sub-field definition is relaxed to
preceeding Contact field is one of those defined for use with the accept all of the discrete "top-level" media types defined in [4]. In
Network Type "TN", the following values are defined for the Transport the milestone services the discrete type "video" is not used, and the
Protocol sub-field: extra types "data" and "control" are likewise not needed. The use of
"voice", "fax", and "pager". these types is not precluded, but the behaviour expected of a PINT
Gateway receiving a request including such a type is not defined
here.
The interpretation of this sub-field within PINT requests is the The Port sub-field has no meaning in PINT requests as the destination
treatment or disposition of the resulting GSTN service. Thus, for terminals are specified using "TN" addressing, so the value of the
transport protocol "voice", the intent is that the service will result port sub-field in PINT requests is normally set to "1". A value of
in a GSTN voice call, whilst for protocol "fax" the result will be a "0" may be used as in SDP to indicate that the terminal is not
GSTN fax transmission, and protocol "pager" will result in a pager receiving media. This is useful to indicate that a telephone
message being sent. terminal has gone "on hold" temporarily. Likewise, the optional
integer sub-field is not used in PINT.
Note that this sub-field does not necessarily dictate the media type and As mentioned in [2], the Transport Protocol sub-field is specific to
subtype of any source data; for example, one of the milestone services the associated Address Type. In the case that the Address Type in the
calls for a textual source to be vocoded and spoken in a resulting preceeding Contact field is one of those defined for use with the
telephone service call. The transport protocol value in this case would Network Type "TN", the following values are defined for the Transport
be "voice", whilst the media type would be "text". Protocol sub-field:
The Fmt sub-field is described in [2] as being transport "voice", "fax", and "pager".
protocol-specific. When used within PINT requests having one of the
above protocol values, this sub-field consists of a list of one or more
values, each of which is a defined MIME sub-type of the associated Media
sub-field value. The special value "-" is allowed, meaning that there
is no MIME sub-type. This sub-field retains (from [2]) its meaning that
the list will contain a set of alternative sub-types, with the first
being the preferred value.
For experimental purposes and by mutual consent of the sender and The interpretation of this sub-field within PINT requests is the
recipient, a sub-type value may be specified as an <X-token>, i.e. a treatment or disposition of the resulting GSTN service. Thus, for
character string starting with "X-". The use of such values is transport protocol "voice", the intent is that the service will
discouraged, and if such a value is expected to find common use then it result in a GSTN voice call, whilst for protocol "fax" the result
SHOULD be registered with IANA using the standard content type will be a GSTN fax transmission, and protocol "pager" will result in
registration process (see Appendix C). a pager message being sent.
When the Fmt parameter is the single character "-" ( a dash ), this is Note that this sub-field does not necessarily dictate the media type
interpreted as meaning that a unspecified or default sub-type can be and subtype of any source data; for example, one of the milestone
used for this service. Thus, the media field value "m=audio 1 voice services calls for a textual source to be vocoded and spoken in a
-<CRLF>" is taken to mean that a voice call is requested, using whatever resulting telephone service call. The transport protocol value in
audio sub type is deemed appropriate by the Executive System. PINT this case would be "voice", whilst the media type would be "text".
service is a special case, in that the request comes from the IP network
but the service call is provided within the GSTN. Thus the service The Fmt sub-field is described in [2] as being transport protocol-
request will not normally be able to define the particular codec used specific. When used within PINT requests having one of the above
for the resulting GSTN service call. If such an intent IS required, then protocol values, this sub-field consists of a list of one or more
the quality attribute may be used (see "Suggested Attributes" section of values, each of which is a defined MIME sub-type of the associated
[2]). Media sub-field value. The special value "-" is allowed, meaning that
there is no MIME sub-type. This sub-field retains (from [2]) its
meaning that the list will contain a set of alternative sub-types,
with the first being the preferred value.
For experimental purposes and by mutual consent of the sender and
recipient, a sub-type value may be specified as an <X-token>, i.e. a
character string starting with "X-". The use of such values is
discouraged, and if such a value is expected to find common use then
it SHOULD be registered with IANA using the standard content type
registration process (see Appendix C).
When the Fmt parameter is the single character "-" ( a dash ), this
is interpreted as meaning that a unspecified or default sub-type can
be used for this service. Thus, the media field value "m=audio 1
voice -<CRLF>" is taken to mean that a voice call is requested, using
whatever audio sub type is deemed appropriate by the Executive
System. PINT service is a special case, in that the request comes
from the IP network but the service call is provided within the GSTN.
Thus the service request will not normally be able to define the
particular codec used for the resulting GSTN service call. If such an
intent IS required, then the quality attribute may be used (see
"Suggested Attributes" section of [2]).
3.4.2.1. Use of fmtp attributes in PINT requests 3.4.2.1. Use of fmtp attributes in PINT requests
For each element of the Fmt sub-field, there MUST be a following fmtp For each element of the Fmt sub-field, there MUST be a following fmtp
attribute. When used within PINT requests, the fmtp attribute has a attribute. When used within PINT requests, the fmtp attribute has a
general structure as defined here: general structure as defined here:
"a=fmtp:" <subtype> <space> resolution
*(<space> resolution)
(<space> ";" 1(<attribute>)
*(<space> <attribute>))
where:
<resolution> := (<uri-ref> | <opaque-ref> | <sub-part-ref>)
A fmtp attribute describes the sources used with a given Fmt entry in "a=fmtp:" <subtype> <space> resolution
the Media field. The entries in a Fmt sub-field are alternatives (with *(<space> resolution)
the preferred one first in the list). Each entry will have a matching (<space> ";" 1(<attribute>)
fmtp attribute. The list of resolutions in a fmtp attribute describes *(<space> <attribute>))
the set of sources that resolve the matching Fmt choice; all elements of where:
this set will be used. <resolution> := (<uri-ref> | <opaque-ref> | <sub-part-ref>)
It should be noted that, for use in PINT services, the elements in such A fmtp attribute describes the sources used with a given Fmt entry in
a set will be sent as a sequence; it is unlikely that trying to send the Media field. The entries in a Fmt sub-field are alternatives
them in parallel would be successful. (with the preferred one first in the list). Each entry will have a
matching fmtp attribute. The list of resolutions in a fmtp attribute
describes the set of sources that resolve the matching Fmt choice;
all elements of this set will be used.
A fmtp attribute can contain a mixture of different kinds of element. It should be noted that, for use in PINT services, the elements in
Thus an attribute might contain a sub-part-ref indicating included data such a set will be sent as a sequence; it is unlikely that trying to
held in a sub-part of the current message, followed by an opaque-ref send them in parallel would be successful.
referring to some content on the GSTN, followed by a uri-ref pointing to
some data held externally on the IP network.
To indicate which form each resolution element takes, each of them A fmtp attribute can contain a mixture of different kinds of element.
starts with its own literal tag. The detailed syntax of each form is Thus an attribute might contain a sub-part-ref indicating included
described in the following sub-sections. data held in a sub-part of the current message, followed by an
opaque-ref referring to some content on the GSTN, followed by a uri-
ref pointing to some data held externally on the IP network.
3.4.2.2. Support for Remote Data Object References in PINT Where data To indicate which form each resolution element takes, each of them
objects stored elsewhere on the IP Network are to be used as sources for starts with its own literal tag. The detailed syntax of each form is
processing within a PINT service, they may be referred to using the described in the following sub-sections.
uri-ref form. This is simply a Uniform Resource Identifier (URI), as
described in [9].
Note that the reference SHOULD be an absolute URI, as there may not be 3.4.2.2. Support for Remote Data Object References in PINT
enough contextual information for the recipient server to resolve a
relative reference; any use of relative references requires some private
agreement between the sender and recipient of the message, and SHOULD be
avoided unless the sender can be sure that the recipient is the one
intended and the reference is unambiguous in context.
This also holds for partial URIs (such as"uri:http://aNode/index.htm") Where data objects stored elsewhere on the IP Network are to be used
as these will need to be resolved in the context of the eventual as sources for processing within a PINT service, they may be referred
recipient of the message. to using the uri-ref form. This is simply a Uniform Resource
Identifier (URI), as described in [9].
The general syntax of a reference to an Internet-based external data Note that the reference SHOULD be an absolute URI, as there may not
object in a fmtp line within a PINT session description is: be enough contextual information for the recipient server to resolve
<uri-ref> := ("uri:" URI-reference) a relative reference; any use of relative references requires some
private agreement between the sender and recipient of the message,
and SHOULD be avoided unless the sender can be sure that the
recipient is the one intended and the reference is unambiguous in
context.
where URI-reference is as defined in Appendix A of [9] This also holds for partial URIs (such
as"uri:http://aNode/index.htm") as these will need to be resolved in
the context of the eventual recipient of the message.
For example: The general syntax of a reference to an Internet-based external data
c= TN RFC2543 +1-201-406-4090 object in a fmtp line within a PINT session description is:
m= text 1 fax plain
a=fmtp:plain uri:ftp://ftp.isi.edu/in-notes/rfc2468.txt
or:
c= TN RFC2543 +1-201-406-4090
m= text 1 fax plain
a=fmtp:plain
uri:http://www.ietf.org/meetings/glance_minneapolis.txt
means get this data object from the Internet and use it as a source for <uri-ref> := ("uri:" URI-reference)
the requested GSTN Fax service.
where URI-reference is as defined in Appendix A of [9]
For example:
c= TN RFC2543 +1-201-406-4090
m= text 1 fax plain
a=fmtp:plain uri:ftp://ftp.isi.edu/in-notes/rfc2468.txt
or:
c= TN RFC2543 +1-201-406-4090
m= text 1 fax plain
a=fmtp:plain
uri:http://www.ietf.org/meetings/glance_minneapolis.txt
means get this data object from the Internet and use it as a source
for the requested GSTN Fax service.
3.4.2.3. Support for GSTN-based Data Objects in PINT 3.4.2.3. Support for GSTN-based Data Objects in PINT
PINT services may refer to data that are held not on the IP Network but PINT services may refer to data that are held not on the IP Network
instead within the GSTN. The way in which these items are indicated need but instead within the GSTN. The way in which these items are
have no meaning within the context of the Requestor or the PINT Gateway; indicated need have no meaning within the context of the Requestor or
the reference is merely some data that may be used by the Executive the PINT Gateway; the reference is merely some data that may be used
System to indicate the content intended as part of the request. These by the Executive System to indicate the content intended as part of
data form an opaque reference, in that they are sent "untouched" through the request. These data form an opaque reference, in that they are
the PINT infrastructure. sent "untouched" through the PINT infrastructure.
A reference to some data object held on the GSTN has the general A reference to some data object held on the GSTN has the general
definition: definition:
<opaque-ref> := ("opr:" *uric)
where uric is as defined in Appendix A of [9]. <opaque-ref> := ("opr:" *uric)
For example: where uric is as defined in Appendix A of [9].
c= TN RFC2543 +1-201-406-4090
m= text 1 fax plain
a=fmtp:plain opr:APPL.123.456
means send the data that is indexed ON THE GSTN by the reference value For example:
"APPL.123.456" to the fax machine on +1-201-406-4090. The Executive
System may also take the Telephone URL held in the To: field of the
enclosing SIP message into account when deciding the context to be used
for the data object dereference.
Of course, an opaque reference may also be used for other purposes; it c= TN RFC2543 +1-201-406-4090
could, for example, be needed to authorise access to a document held on m= text 1 fax plain
the GSTN rather than being required merely to disambiguate the data a=fmtp:plain opr:APPL.123.456
object. The purpose to which an opaque reference is put, however, is out
of scope for this document. It is merely an indicator carried within a
PINT Request.
An opaque reference may have no value in the case where the value to be means send the data that is indexed ON THE GSTN by the reference
used is implicit in the rest of the request. For example, suppose some value "APPL.123.456" to the fax machine on +1-201-406-4090. The
company wishes to use PINT to implement a "fax-back service". In their Executive System may also take the Telephone URL held in the To:
current implementation, the image(s) to be faxed are entirely defined by field of the enclosing SIP message into account when deciding the
the telephone number dialled. Within the PINT request, this telephone context to be used for the data object dereference.
number would appear within the "To:" field of the PINT request, and so
there is no need for an opaque reference value.
If there are several resolutions for a PINT Service Request, and one of Of course, an opaque reference may also be used for other purposes;
these is an opaque reference with no value, then that opaque reference it could, for example, be needed to authorise access to a document
MUST be included in the attribute line, but with an empty value field. held on the GSTN rather than being required merely to disambiguate
the data object. The purpose to which an opaque reference is put,
however, is out of scope for this document. It is merely an indicator
carried within a PINT Request.
For example: An opaque reference may have no value in the case where the value to
c= TN RFC2543 +1-201-406-4090 be used is implicit in the rest of the request. For example, suppose
m= text 1 fax plain some company wishes to use PINT to implement a "fax-back service". In
a=fmtp:plain uri:http://www.sun.com/index.html opr: their current implementation, the image(s) to be faxed are entirely
defined by the telephone number dialled. Within the PINT request,
this telephone number would appear within the "To:" field of the PINT
request, and so there is no need for an opaque reference value.
might be used to precede some data to be faxed with a covering note. If there are several resolutions for a PINT Service Request, and one
of these is an opaque reference with no value, then that opaque
reference MUST be included in the attribute line, but with an empty
value field.
In the special case where an opaque reference is the sole resolution of For example:
a PINT Service Request, AND that reference needs no value, there is no
need for a Fmt list at all; the intent of the service is unambiguous
without any further resolution.
For example: c= TN RFC2543 +1-201-406-4090
c= TN RFC2543 +1-201-406-4090 m= text 1 fax plain
m= text 1 fax - a=fmtp:plain uri:http://www.sun.com/index.html opr:
means that there is an implied content stored on the GSTN, and that this might be used to precede some data to be faxed with a covering note.
is uniquely identified by the combination of SIP To-URI and the Contact
field of the session description. In the special case where an opaque reference is the sole resolution
of a PINT Service Request, AND that reference needs no value, there
is no need for a Fmt list at all; the intent of the service is
unambiguous without any further resolution.
For example:
c= TN RFC2543 +1-201-406-4090
m= text 1 fax -
means that there is an implied content stored on the GSTN, and that
this is uniquely identified by the combination of SIP To-URI and the
Contact field of the session description.
3.4.2.4. Session Description support for included Data Objects 3.4.2.4. Session Description support for included Data Objects
As an alternative to pointing to the data via a URI or an opaque As an alternative to pointing to the data via a URI or an opaque
reference to a data item held on the GSTN, it is possible to include the reference to a data item held on the GSTN, it is possible to include
content data within the SIP request itself. This is done by using the content data within the SIP request itself. This is done by using
multipart MIME for the SIP payload. The first MIME part contains the SDP multipart MIME for the SIP payload. The first MIME part contains the
description of the telephone network session to be executed. The other SDP description of the telephone network session to be executed. The
MIME parts contain the content data to be transported. other MIME parts contain the content data to be transported.
Format specific attribute lines within the session description are used Format specific attribute lines within the session description are
to indicate which other MIME part within the request contains the used to indicate which other MIME part within the request contains
content data. Instead of a URI or opaque reference, the format-specific the content data. Instead of a URI or opaque reference, the format-
attribute indicates the Content-ID of the MIME part of the request that specific attribute indicates the Content-ID of the MIME part of the
contains the actual data, and is defined as: request that contains the actual data, and is defined as:
<sub-part-ref> := ("spr:" Content-ID)
where Content-ID is as defined in Appendix A of [3] and in [10]).
For example: <sub-part-ref> := ("spr:" Content-ID)
c= TN RFC2543 +1-201-406-4090
m= text 1 fax plain
a=fmtp:plain spr:<Content-ID>
The <Content-ID> parameter is the Content-ID of one of the MIME parts where Content-ID is as defined in Appendix A of [3] and in [10]).
inside the message, and this fragment means that the requesting user
would like the data object held in the sub-part of this message labelled
<Content-ID> to be faxed to the machine at phone number +1-201-406-4090.
See also section 3.5.1 for a discussion on the support needed in the For example:
enclosing SIP request for included data objects.
c= TN RFC2543 +1-201-406-4090
m= text 1 fax plain
a=fmtp:plain spr:<Content-ID>
The <Content-ID> parameter is the Content-ID of one of the MIME parts
inside the message, and this fragment means that the requesting user
would like the data object held in the sub-part of this message
labelled <Content-ID> to be faxed to the machine at phone number +1-
201-406-4090.
See also section 3.5.1 for a discussion on the support needed in the
enclosing SIP request for included data objects.
3.4.3. Attribute Tags to pass information into the Telephone Network 3.4.3. Attribute Tags to pass information into the Telephone Network
It may be desired to include within the PINT request service parameters It may be desired to include within the PINT request service
that can be understood only by some entity in the "Telephone Network parameters that can be understood only by some entity in the
Cloud". SDP attribute parameters are used for this purpose. They MAY "Telephone Network Cloud". SDP attribute parameters are used for this
appear within a particular media description or outside of a media purpose. They MAY appear within a particular media description or
description. outside of a media description.
These attributes may also appear as parameters within PINT URLS (see These attributes may also appear as parameters within PINT URLS (see
section 3.5.6) as part of a SIP request. section 3.5.6) as part of a SIP request.
This is necessary so that telephone terminals that require the This is necessary so that telephone terminals that require the
attributes to be defined can appear within the To: line of a PINT attributes to be defined can appear within the To: line of a PINT
request as well as within PINT session descriptions. request as well as within PINT session descriptions.
The purpose of these attributes is to allow the client to specify extra The purpose of these attributes is to allow the client to specify
context within which a particular telephone number is to be interpreted. extra context within which a particular telephone number is to be
There are many reasons why extra context might be necessary to interpret interpreted. There are many reasons why extra context might be
a given telephone number: necessary to interpret a given telephone number:
a. The telephone number might be reachable in many different ways
(such as via competing telephone service providers), and the PINT
client wishes to indicate its selection of service provider.
b. The telephone number might be reachable only from a limited
number of networks (such as an '800' freephone number).
c. The telephone number might be reachable only within a a. The telephone number might be reachable in many different ways
single telephone network (such as the '152' customer service (such as via competing telephone service providers), and the
number of BT). Similarly, the number might be an internal PINT client wishes to indicate its selection of service
corporate extension reachable only within the PBX. provider.
b. The telephone number might be reachable only from a limited
number of networks (such as an '800' freephone number).
c. The telephone number might be reachable only within a single
telephone network (such as the '152' customer service number of
BT). Similarly, the number might be an internal corporate
extension reachable only within the PBX.
However, as noted above, it is not usually necessary to use SDP However, as noted above, it is not usually necessary to use SDP
attributes to specify the phone context. URLs such as 152@pint.bt.co.il attributes to specify the phone context. URLs such as
within the To: and From: headers and/or Request-URI, normally offer 152@pint.bt.co.il within the To: and From: headers and/or Request-
sufficient context to resolve telephone numbers. URI, normally offer sufficient context to resolve telephone numbers.
If the client wishes the request to fail if the attributes are not If the client wishes the request to fail if the attributes are not
supported, these attributes SHOULD be used in conjunction with the supported, these attributes SHOULD be used in conjunction with the
"require" attribute (section 3.4.4) and the "require" attribute (section 3.4.4) and the
"Require:org.ietf.sdp.require" header (section 3.5.4). "Require:org.ietf.sdp.require" header (section 3.5.4).
It is not possible to standardise every possible internal telephone It is not possible to standardise every possible internal telephone
network parameter. PINT 1.0 attributes have been chosen for network parameter. PINT 1.0 attributes have been chosen for
specification because they are common enough that many different PINT specification because they are common enough that many different PINT
systems will want to use them, and therefore interoperability will be systems will want to use them, and therefore interoperability will be
increased by having a single specification. increased by having a single specification.
Proprietary attribute "a=" lines, that by definition are not Proprietary attribute "a=" lines, that by definition are not
interoperable, may be nonetheless useful when it is necessary to interoperable, may be nonetheless useful when it is necessary to
transport some proprietary internal telephone network variables over the transport some proprietary internal telephone network variables over
IP network, for example to identify the order in which service call legs the IP network, for example to identify the order in which service
are to be be made. These private attributes SHOULD BE, however, subject call legs are to be be made. These private attributes SHOULD BE,
to the same IANA registration procedures mentioned in the SDP however, subject to the same IANA registration procedures mentioned
specification[2] (see also this Appendix C). in the SDP specification[2] (see also this Appendix C).
3.4.3.1. The phone-context attribute 3.4.3.1. The phone-context attribute
An attribute is specified to enable "remote local dialling". This is the An attribute is specified to enable "remote local dialling". This is
service that allows a PINT client to reach a number from far outside the the service that allows a PINT client to reach a number from far
area or network that can usually reach the number. It is useful when the outside the area or network that can usually reach the number. It is
sending or receiving address is only dialable within some local context, useful when the sending or receiving address is only dialable within
which may be remote to the origin of the PINT client. some local context, which may be remote to the origin of the PINT
client.
For example, if Alice wanted to report a problem with her telephone, she For example, if Alice wanted to report a problem with her telephone,
might then dial a "network wide" customer care number; within the she might then dial a "network wide" customer care number; within the
British Telecom network in the U.K., this is "152". Note that in this British Telecom network in the U.K., this is "152". Note that in this
case she doesn't dial any trunk prefix - this is the whole dialable case she doesn't dial any trunk prefix - this is the whole dialable
number. If dialled from another operator's network, it will not connect number. If dialled from another operator's network, it will not
to British Telecom's Engineering Enquiries service; and dialling "+44 connect to British Telecom's Engineering Enquiries service; and
152" will not normally succeed. Such numbers are called Network-Specific dialling "+44 152" will not normally succeed. Such numbers are called
Service Numbers. Network-Specific Service Numbers.
Within the telephone network, the "local context" is provided by the Within the telephone network, the "local context" is provided by the
physical connection between the subscriber's terminal and the central physical connection between the subscriber's terminal and the central
office. An analogous association between the PINT client and the PINT office. An analogous association between the PINT client and the PINT
server that first receives the request may not exist, which is why it server that first receives the request may not exist, which is why it
may be necessary to supply this missing "telephone network context". may be necessary to supply this missing "telephone network context".
This attribute is defined as follows: This attribute is defined as follows:
a=phone-context: <phone-context-ident>
phone-context-ident = network-prefix / private-prefix
network-prefix = intl-network-prefix / local-network-prefix
intl-network-prefix = "+" 1*DIGIT
local-network-prefix = 1*DIGIT
excldigandplus = (0x21-0x2d,0x2f,0x40-0x7d))
private-prefix = 1*excldigandplus 0*uric
An intl-network-prefix and local-network-prefix MUST be a bona fide a=phone-context: <phone-context-ident>
network prefix, and a network-prefix that is an intl-network-prefix MUST phone-context-ident = network-prefix / private-prefix
begin with an E.164 service code ("country code"). network-prefix = intl-network-prefix / local-network-prefix
intl-network-prefix = "+" 1*DIGIT
local-network-prefix = 1*DIGIT
excldigandplus = (0x21-0x2d,0x2f,0x40-0x7d))
private-prefix = 1*excldigandplus 0*uric
It is possible to register new private-prefixes with IANA so as to avoid An intl-network-prefix and local-network-prefix MUST be a bona fide
collisions. Prefixes that are not so registered MUST begin with an "X-" network prefix, and a network-prefix that is an intl-network-prefix
to indicate their private, non-standard nature (see Appendix C). MUST begin with an E.164 service code ("country code").
Example 1: It is possible to register new private-prefixes with IANA so as to
avoid collisions. Prefixes that are not so registered MUST begin with
an "X-" to indicate their private, non-standard nature (see Appendix
C).
c= TN RFC2543 1-800-765-4321 Example 1:
a=phone-context:+972
This describes an terminal whose address in Israel (E.164 country code c= TN RFC2543 1-800-765-4321
972) is 1-800-765-4321. a=phone-context:+972
Example 2: This describes an terminal whose address in Israel (E.164 country
code 972) is 1-800-765-4321.
c= TN RFC2543 1-800-765-4321 Example 2:
a=phone-context:+1
This describes an terminal whose address in North America (E.164 country c= TN RFC2543 1-800-765-4321
code 1) is 1-800-765-4321. a=phone-context:+1
The two telephone terminals described by examples 1 and 2 are different; This describes an terminal whose address in North America (E.164
in fact they are located in different countries. country code 1) is 1-800-765-4321.
Example 3: The two telephone terminals described by examples 1 and 2 are
different; in fact they are located in different countries.
c=TN RFC2543 123 Example 3:
a=phone-context:+97252
This describes a terminal whose address when dialled from within the c=TN RFC2543 123
network identified by +97252 is the string "123". It so happens that a=phone-context:+97252
+97252 defines one of the Israeli cell phone providers, and 123 reaches
customer service when dialled within that network.
It may well be useful or necessary to use the SDP "require" parameter in This describes a terminal whose address when dialled from within the
conjunction with the phone-context attribute. network identified by +97252 is the string "123". It so happens that
+97252 defines one of the Israeli cell phone providers, and 123
reaches customer service when dialled within that network.
Example 4: It may well be useful or necessary to use the SDP "require" parameter
in conjunction with the phone-context attribute.
c= TN RFC2543 321 Example 4:
a=phone-context:X-acme.com-23
This might describe the telephone terminal that is at extension 321 of c= TN RFC2543 321
PBX number 23 within the acme.com private PBX network. It is expected a=phone-context:X-acme.com-23
that such a description would be understandable by the acme.com PINT
server that receives the request.
Note that if the PINT server receiving the request is inside the This might describe the telephone terminal that is at extension 321
acme.com network, the same terminal might be addressable as follows: of PBX number 23 within the acme.com private PBX network. It is
expected that such a description would be understandable by the
acme.com PINT server that receives the request.
c= TN RFC2543 7-23-321 Note that if the PINT server receiving the request is inside the
acme.com network, the same terminal might be addressable as follows:
(assuming that "7" is dialled in order to reach the private PBX network c= TN RFC2543 7-23-321
from within acme.com)
(assuming that "7" is dialled in order to reach the private PBX
network from within acme.com)
3.4.3.2. Presentation Restriction attribute 3.4.3.2. Presentation Restriction attribute
Although it has no affect on the transport of the service request Although it has no affect on the transport of the service request
through the IP Network, there may be a requirement to allow originators through the IP Network, there may be a requirement to allow
of a PINT service request to indicate whether or not they wish the "B originators of a PINT service request to indicate whether or not they
party" in the resulting service call to be presented with the "A wish the "B party" in the resulting service call to be presented with
party's" calling telephone number. It is a legal requirement in some the "A party's" calling telephone number. It is a legal requirement
jurisdictions that a caller be able to select whether or not their in some jurisdictions that a caller be able to select whether or not
correspondent can find out the calling telephone number (using Automatic their correspondent can find out the calling telephone number (using
Number Indication or Caller Display or Calling Line Identity Automatic Number Indication or Caller Display or Calling Line
Presentation equipment). Thus an attribute may be needed to indicate the Identity Presentation equipment). Thus an attribute may be needed to
originator's preference. indicate the originator's preference.
Whether or not the default behaviour of the Executive System is to Whether or not the default behaviour of the Executive System is to
present or not present a party's telephone number to the correspondent present or not present a party's telephone number to the
GSTN terminal is not specified, and it is not mandatory in all correspondent GSTN terminal is not specified, and it is not mandatory
territories for a PINT Gateway or Executive System to act on this in all territories for a PINT Gateway or Executive System to act on
attribute. It is, however, defined here for use where there are this attribute. It is, however, defined here for use where there are
regulatory restrictions on GSTN operation, and in that case the regulatory restrictions on GSTN operation, and in that case the
Executive System can use it to honour the originator's request. Executive System can use it to honour the originator's request.
The attribute is specified as follows: The attribute is specified as follows:
a=clir:<"true" | "false"> a=clir:<"true" | "false">
This boolean value is needed within the attribute as it may be that the This boolean value is needed within the attribute as it may be that
GSTN address is, by default, set to NOT present its identity to the GSTN address is, by default, set to NOT present its identity to
correspondents, and the originator wants to do so for this particular correspondents, and the originator wants to do so for this particular
call. It is in keeping with the aim of this attribute to allow the call. It is in keeping with the aim of this attribute to allow the
originator to specify what treatment they want for the requested service originator to specify what treatment they want for the requested
call. service call.
The expected interpretation of this attribute is that, if it is present The expected interpretation of this attribute is that, if it is
and the value is "false" then the Calling Line Identity CAN be presented present and the value is "false" then the Calling Line Identity CAN
to the correspondent terminal, whilst if it is "true" then it if be presented to the correspondent terminal, whilst if it is "true"
possible the Executive System is requested to NOT present the Calling then if possible the Executive System is requested to NOT present the
Line Identity. Calling Line Identity.
3.4.3.3. ITU-T CalledPartyAddress attributes parameters 3.4.3.3. ITU-T CalledPartyAddress attributes parameters
These attributes correspond to fields that appear within the ITU-T Q.763 These attributes correspond to fields that appear within the ITU-T
"CalledPartyAddress" field (see [8] ,section 3.9). PINT clients use Q.763 "CalledPartyAddress" field (see [8] ,section 3.9). PINT clients
these attributes in order to specify further parameters relating to use these attributes in order to specify further parameters relating
Terminal Addresses, in the case when the address indicates a to Terminal Addresses, in the case when the address indicates a
"local-phone-number". In the case that the PINT request contains a "local-phone-number". In the case that the PINT request contains a
reference to a GSTN terminal, the parameters may be required to reference to a GSTN terminal, the parameters may be required to
correctly identify that remote terminal. correctly identify that remote terminal.
The general form of this attribute is:
"a=Q763-<token>((":" <value>) |"")".
Three of the possible elements and their use in SDP attributes are
described here. Where other Q763 elements are to be used, then these
should be the subject of further specification to define the syntax of
the attribute mapping. It is recommended that any such specification
maintains the value sets shown in Q.763.
The defined attributes are: The general form of this attribute is: "a=Q763-<token>((":" <value>)
|"")". Three of the possible elements and their use in SDP
attributes are described here. Where other Q763 elements are to be
used, then these should be the subject of further specification to
define the syntax of the attribute mapping. It is recommended that
any such specification maintains the value sets shown in Q.763.
a=Q763-nature: - indicates the "nature of address indicator". The defined attributes are:
The value MAY be any number between 0 and 127.
The following values are specified:
"1" a subscriber number a=Q763-nature: - indicates the "nature of address indicator".
"2" unknown The value MAY be any number between 0 and 127.
"3" a nationally significant number The following values are specified:
"4" an internationally significant number
The values have been chosen to coincide with the values in Q.763. Note "1" a subscriber number
that other values are possible, according to national rules or future "2" unknown
expansion of Q.763. "3" a nationally significant number
"4" an internationally significant number
a=Q763-plan: - indicates the numbering plan to which the address The values have been chosen to coincide with the values in Q.763.
belongs. The value MAY be any number between 0 and Note that other values are possible, according to national rules or
7. The following values are specified: future expansion of Q.763.
"1" Telephone numbering plan (ITU-T E.164) a=Q763-plan: - indicates the numbering plan to which the address
"3" Data numbering plan (ITU-T X.121) belongs. The value MAY be any number between 0
"4" Telex numbering plan (ITU-T F.69) and 7. The following values are specified:
The values have been chosen to coincide with the values in Q.763. Other "1" Telephone numbering plan (ITU-T E.164)
values are allowed, according to national rules or future expansion of "3" Data numbering plan (ITU-T X.121)
Q.763. "4" Telex numbering plan (ITU-T F.69)
a=Q763-INN - indicates if routing to the Internal Network Number The values have been chosen to coincide with the values in Q.763.
is allowed. The value MUST be ONE of: Other values are allowed, according to national rules or future
expansion of Q.763.
"0" routing to internal network number allowed a=Q763-INN - indicates if routing to the Internal Network Number
"1" routing to internal network number not is allowed. The value MUST be ONE of:
allowed
The values have been chosen to coincide with the values in Q.763. "0" routing to internal network number allowed
"1" routing to internal network number not
allowed
Note that it is possible to use a local-phone-number and indicate via The values have been chosen to coincide with the values in Q.763.
attributes that the number is in fact an internationally significant Note that it is possible to use a local-phone-number and indicate via
E.164 number. Normally this SHOULD NOT be done; an internationally attributes that the number is in fact an internationally significant
significant E.164 number is indicated by using a "global-phone-number" E.164 number. Normally this SHOULD NOT be done; an internationally
for the address string. significant E.164 number is indicated by using a "global-phone-
number" for the address string.
3.4.4. The "require" attribute 3.4.4. The "require" attribute
According to the SDP specification, a PINT server is allowed simply to According to the SDP specification, a PINT server is allowed simply
ignore attribute parameters that it does not understand. In order to to ignore attribute parameters that it does not understand. In order
force a server to decline a request if it does not understand one of the to force a server to decline a request if it does not understand one
PINT attributes, a client SHOULD use the "require" attribute, specified of the PINT attributes, a client SHOULD use the "require" attribute,
as follows: specified as follows:
a=require:<attribute-list> a=require:<attribute-list>
where the attribute-list is a comma-separated list of attributes that where the attribute-list is a comma-separated list of attributes that
appear elsewhere in the session description. appear elsewhere in the session description.
In order to process the request successfully the PINT server must BOTH In order to process the request successfully the PINT server must
understand the attribute AND ALSO fulfil the request implied by the BOTH understand the attribute AND ALSO fulfill the request implied by
presence of the attribute, for each attribute appearing within the the presence of the attribute, for each attribute appearing within
attribute-list of the require attribute. the attribute-list of the require attribute.
If the server does not recognise the attribute listed, the PINT server If the server does not recognise the attribute listed, the PINT
MUST return an error status code (such as 420 (Bad Extension) or 400 server MUST return an error status code (such as 420 (Bad Extension)
(Bad Request)), and SHOULD return suitable Warning: lines explaining the or 400 (Bad Request)), and SHOULD return suitable Warning: lines
problem or an Unsupported: header containing the attribute it does not explaining the problem or an Unsupported: header containing the
understand. If the server recognizes the attribute listed, but cannot attribute it does not understand. If the server recognizes the
fulfil the request implied by the presence of the attribute, the request attribute listed, but cannot fulfill the request implied by the
MUST be rejected with a status code of (606 Not Acceptable), along with presence of the attribute, the request MUST be rejected with a status
a suitable Unsupported: header or Warning: line. code of (606 Not Acceptable), along with a suitable Unsupported:
header or Warning: line.
The "require" attribute may appear anywhere in the session description, The "require" attribute may appear anywhere in the session
and any number of times, but it MUST appear before the use of the description, and any number of times, but it MUST appear before the
attribute marked as required. use of the attribute marked as required.
Since the "require" attribute is itself an attribute, the SIP Since the "require" attribute is itself an attribute, the SIP
specification allows a server that does not understand the require specification allows a server that does not understand the require
attribute to ignore it. In order to ensure that the PINT server will attribute to ignore it. In order to ensure that the PINT server will
comply with the "require" attribute, a PINT client SHOULD include a comply with the "require" attribute, a PINT client SHOULD include a
Require: header with the tag "ietf.org.sdp.require" (section 3.5.4) Require: header with the tag "org.ietf.sdp.require" (section 3.5.4)
Note that the majority of the PINT extensions are "tagged" and these Note that the majority of the PINT extensions are "tagged" and these
tags can be included in Require strictures. The exception is the use of tags can be included in Require strictures. The exception is the use
phone numbers in SDP parts. However, these are defined as a new network of phone numbers in SDP parts. However, these are defined as a new
and address type, so that a receiving SIP/SDP server should be able to network and address type, so that a receiving SIP/SDP server should
detect whether or not it supports these forms. The default behaviour for be able to detect whether or not it supports these forms. The default
any SDP recipient is that it will fail a PINT request if it does not behaviour for any SDP recipient is that it will fail a PINT request
recognise or support the TN and RFC2543 or X-token network and address if it does not recognise or support the TN and RFC2543 or X-token
types, as without the contents being recognised no media session could network and address types, as without the contents being recognised
be created. Thus a separate stricture is not required in this case. no media session could be created. Thus a separate stricture is not
required in this case.
3.5. PINT Extensions to SIP 2.0 3.5. PINT Extensions to SIP 2.0
PINT requests are SIP requests; Many of the specifications within this PINT requests are SIP requests; Many of the specifications within
document merely explain how to use existing SIP facilities for the this document merely explain how to use existing SIP facilities for
purposes of PINT. the purposes of PINT.
3.5.1. Multi-part MIME (sending data along with SIP request) 3.5.1. Multi-part MIME (sending data along with SIP request)
A PINT request can contain a payload which is multipart MIME. In this A PINT request can contain a payload which is multipart MIME. In this
case the first part MUST contain an SDP session description that case the first part MUST contain an SDP session description that
includes at least one of the format specific attribute tags for includes at least one of the format specific attribute tags for
"included content data" specified above in section 3.4.3. Subsequent "included content data" specified above in section 3.4.3. Subsequent
parts contain content data that may be transferred to the requested parts contain content data that may be transferred to the requested
Telephone Call Service. As discussed earlier, within a single PINT Telephone Call Service. As discussed earlier, within a single PINT
request, some of the data MAY be pointed to by a URI within the request, request, some of the data MAY be pointed to by a URI within the
and some of the data MAY be included within the request. request, and some of the data MAY be included within the request.
Where included data is carried within a PINT service request, the Where included data is carried within a PINT service request, the
Content Type entity header of the enclosing SIP message MUST indicate Content Type entity header of the enclosing SIP message MUST indicate
this. To do so, the media type value within this entity header MUST be this. To do so, the media type value within this entity header MUST
set to a value of "multipart". There is a content sub-type that is be set to a value of "multipart". There is a content sub-type that is
intended for situations like this in which sub-parts are to be handled intended for situations like this in which sub-parts are to be
together. This is the multipart/related type (defined in [19]), and it's handled together. This is the multipart/related type (defined in
use is recommended. [19]), and it's use is recommended.
The enclosed body parts SHOULD include the part-specific Content Type The enclosed body parts SHOULD include the part-specific Content Type
headers as appropriate ("application/sdp" for the first body part headers as appropriate ("application/sdp" for the first body part
holding the session description, with an appropriate content type for holding the session description, with an appropriate content type for
each of the subsequent, "included data object" parts). This matches the each of the subsequent, "included data object" parts). This matches
standard syntax of MIME multipart messages as defined in [4]. the standard syntax of MIME multipart messages as defined in [4].
For example, in a multipart message where the string "------next-------" For example, in a multipart message where the string
is the boundary, the first two parts might be as follows:
------next------- "------next-------" is the boundary, the first two parts might be as
Content-Type: application/sdp follows:
....
c= TN RFC2543 +1-201-406-4090
m= text 1 pager plain
a=fmtp:plain spr:17@mymessage.acme.com
----------next------- ------next-------
Content-Type: text/plain Content-Type: application/sdp
Content-ID: 17@mymessage.acme.com ....
c= TN RFC2543 +1-201-406-4090
m= text 1 pager plain
a=fmtp:plain spr:17@mymessage.acme.com
This is the text that is to be paged to +1-201-406-4090 ----------next-------
Content-Type: text/plain
Content-ID: 17@mymessage.acme.com
----------next----------- This is the text that is to be paged to +1-201-406-4090
The ability to indicate different alternatives for the content to be ----------next-----------
transported is useful, even when the alternatives are included within
the request. For example, a request to send a short message to a pager
might include the message in Unicode [5] and an alternative version of
the same content in text/plain, should the PINT server or telephone
network not be able to process the unicode.
PINT clients should be extremely careful when sending included data The ability to indicate different alternatives for the content to be
within a PINT request. Such requests SHOULD be sent via TCP, to avoid transported is useful, even when the alternatives are included within
fragmentation and to transmit the data reliably. It is possible that the the request. For example, a request to send a short message to a
PINT server is a proxy server that will replicate and fork the request, pager might include the message in Unicode [5] and an alternative
which could be disastrous if the request contains a large amount of version of the same content in text/plain, should the PINT server or
application data. PINT proxy servers should be careful not to create telephone network not be able to process the unicode.
many copies of a request with large amounts of data in it. If the client
does not know the actual location of the PINT gateway, and is using the PINT clients should be extremely careful when sending included data
SIP location services to find it, and the included data makes the PINT within a PINT request. Such requests SHOULD be sent via TCP, to avoid
request likely to be transported in several IP datagrams, it is fragmentation and to transmit the data reliably. It is possible that
RECOMMENDED that the initial PINT request not include the data object the PINT server is a proxy server that will replicate and fork the
but instead hold a reference to it. request, which could be disastrous if the request contains a large
amount of application data. PINT proxy servers should be careful not
to create many copies of a request with large amounts of data in it.
If the client does not know the actual location of the PINT gateway,
and is using the SIP location services to find it, and the included
data makes the PINT request likely to be transported in several IP
datagrams, it is RECOMMENDED that the initial PINT request not
include the data object but instead hold a reference to it.
3.5.2. Warning header 3.5.2. Warning header
A PINT server MUST support the SIP "Warning:" header so that it can A PINT server MUST support the SIP "Warning:" header so that it can
signal lack of support for individual PINT features. As an example, signal lack of support for individual PINT features. As an example,
suppose the PINT request is to send a jpeg picture to a fax machine, but suppose the PINT request is to send a jpeg picture to a fax machine,
the server cannot retrieve and/or translate jpeg pictures from the but the server cannot retrieve and/or translate jpeg pictures from
Internet into fax transmissions. the Internet into fax transmissions.
In such a case the server fails the request and includes a Warning such In such a case the server fails the request and includes a Warning
as the following: such as the following:
Warning: 305 pint.acme.com Incompatible media format: jpeg
SIP servers that do not understand the PINT extensions at all are Warning: 305 pint.acme.com Incompatible media format: jpeg
strongly encouraged to implement Warning: headers to indicate that PINT
extensions are not understood.
Also, Warning: headers may be included within NOTIFY requests if it is SIP servers that do not understand the PINT extensions at all are
necessary to notify the client about some condition concerning the strongly encouraged to implement Warning: headers to indicate that
invocation of the PINT service (see next). PINT extensions are not understood.
Also, Warning: headers may be included within NOTIFY requests if it
is necessary to notify the client about some condition concerning the
invocation of the PINT service (see next).
3.5.3. Mechanism to register interest in the disposition of a PINT 3.5.3. Mechanism to register interest in the disposition of a PINT
service, and to receive indications on that disposition service, and to receive indications on that disposition
It can be very useful to find out whether or not a requested service has It can be very useful to find out whether or not a requested service
completed, and if so whether or not it was successful. This is has completed, and if so whether or not it was successful. This is
especially true for PINT service, where the person requesting the especially true for PINT service, where the person requesting the
service is not (necessarily) a party to it, and so may not have an easy service is not (necessarily) a party to it, and so may not have an
way of finding out the disposition of that service. Equally, it may be easy way of finding out the disposition of that service. Equally, it
useful to indicate when the service has changed state, for example when may be useful to indicate when the service has changed state, for
the service call has started. example when the service call has started.
Arranging a flexible system to provide extensive monitoring and control Arranging a flexible system to provide extensive monitoring and
during a service is non-trivial (see section 6.4 for some issues); PINT control during a service is non-trivial (see section 6.4 for some
1.0 uses a simple scheme that should nevertheless provide useful issues); PINT 1.0 uses a simple scheme that should nevertheless
information. It is possible to expand the scheme in a "backwards provide useful information. It is possible to expand the scheme in a
compatible" manner, so if required it can be enhanced at a later date. "backwards compatible" manner, so if required it can be enhanced at a
Such enhancement would be expected to be the subject of a separate later date.
document.
The PINT 1.0 status registration and indication scheme uses three new The PINT 1.0 status registration and indication scheme uses three new
methods; SUBSCRIBE, UNSUBSCRIBE, and NOTIFY. These are used to allow a methods; SUBSCRIBE, UNSUBSCRIBE, and NOTIFY. These are used to allow
PINT Requesting entity to register an interest in (or "subscribe" to) a PINT client to register an interest in (or "subscribe" to) the
the status of a service request, to indicate that a prior interest has status of a service request, to indicate that a prior interest has
lapsed (i.e "unsubscribe" from the status), and for the gateway to lapsed (i.e "unsubscribe" from the status), and for the server to
return service indications. All of these messages follow the same return service indications. The state machine of
procedure as used for all the SIP requests other than INVITE; the SUBSCRIBE/UNSUBSCRIBE is identical to that of INVITE/BYE; just as
recipient MUST acknowledge the request with a final response message, INVITE signals the beginning and BYE signals the end of participation
otherwise the request will be repeated. in a media session, SUBSCRIBE signals the beginning and UNSUBSCRIBE
signals the end of participation in a monitoring session. During the
monitoring session, NOTIFY messages are sent to inform the subscriber
of a change in session state or disposition.
3.5.3.1. Opening a monitoring session with a SUBSCRIBE request 3.5.3.1. Opening a monitoring session with a SUBSCRIBE request
When a SUBSCRIBE request is sent to a PINT Server, it indicates that a When a SUBSCRIBE request is sent to a PINT Server, it indicates that
user wishes to receive information about the status of a service a user wishes to receive information about the status of a service
session. The request identifies the session of interest by including the session. The request identifies the session of interest by including
original session description along with the request, using the SDP the original session description along with the request, using the
global-session-id that forms part of the origin-field to identify the SDP global-session-id that forms part of the origin-field to identify
service session uniquely. the service session uniquely.
The SUBSCRIBE request (like any other SIP request about an ongoing The SUBSCRIBE request (like any other SIP request about an ongoing
session) is sent to the same server as was sent the original INVITE, session) is sent to the same server as was sent the original INVITE,
or to a server which was specified in the Contact: field within a or to a server which was specified in the Contact: field within a
subsequent response (this might well be the PINT gateway for the subsequent response (this might well be the PINT gateway for the
session). session).
Whilst there are situations in which re-use of the Call-ID used in the Whilst there are situations in which re-use of the Call-ID used in
original INVITE that initiated the session of interest is possible, the original INVITE that initiated the session of interest is
there are other situations in which it is not. In detail, where the possible, there are other situations in which it is not. In detail,
subscription is being made by the user who initiated the original where the subscription is being made by the user who initiated the
service request, the Call-ID may be used as it will be known to the original service request, the Call-ID may be used as it will be known
receiver to refer to a previously established session. However, when the to the receiver to refer to a previously established session.
request comes from a user other than the original requesting user, the However, when the request comes from a user other than the original
SUBSCRIBE request constitutes a new SIP call leg, so the Call-ID SHOULD requesting user, the SUBSCRIBE request constitutes a new SIP call
NOT be used; the only common identifier is the origin-field of the leg, so the Call-ID SHOULD NOT be used; the only common identifier is
session description enclosed within the original service request, and so the origin-field of the session description enclosed within the
this MUST be used. original service request, and so this MUST be used.
Rather than have two different methods of identifying the "session of Rather than have two different methods of identifying the "session of
interest" the choice is to use the origin-field of the SDP sub-part interest" the choice is to use the origin-field of the SDP sub-part
included both in the original INVITE and in this SUBSCRIBE request. included both in the original INVITE and in this SUBSCRIBE request.
Note that the request MUST NOT include any sub-parts other than the Note that the request MUST NOT include any sub-parts other than the
session description, even if these others were present in the original session description, even if these others were present in the
INVITE request. A server MUST ignore whatever sub-parts are included original INVITE request. A server MUST ignore whatever sub-parts are
within a SUBSCRIBE request with the sole exception of the enclosed included within a SUBSCRIBE request with the sole exception of the
session description. enclosed session description.
The request MAY contain a "Contact:" header, specifying the PINT User The request MAY contain a "Contact:" header, specifying the PINT User
Agent Server to which such information should be sent. Agent Server to which such information should be sent.
In addition, it SHOULD contain an Expires: header, which indicates for In addition, it SHOULD contain an Expires: header, which indicates
how long the PINT Requestor wishes to receive notification of the for how long the PINT Requestor wishes to receive notification of the
session status. We refer to the period of time before the expiration of session status. We refer to the period of time before the expiration
the SUBSCRIBE request as the "subscription period". See section 5.1.4. of the SUBSCRIBE request as the "subscription period". See section
for security considerations, particularly privacy implications. 5.1.4. for security considerations, particularly privacy
implications.
A value of 0 within the Expires: header indicates a desire to receive A value of 0 within the Expires: header indicates a desire to receive
one single immediate response (i.e. the request expires immediately). It one single immediate response (i.e. the request expires immediately).
is possible for a sequence of monitoring sessions to be opened, exist, It is possible for a sequence of monitoring sessions to be opened,
and complete, all relating to the same service session. exist, and complete, all relating to the same service session.
A successful response to the SUBSCRIBE request includes the session A successful response to the SUBSCRIBE request includes the session
description, according to the Gateway. Normally this will be identical description, according to the Gateway. Normally this will be
to the last cached response that the Gateway returned to any request identical to the last cached response that the Gateway returned to
concerning the same SDP global session id (see [2], section 6, o= any request concerning the same SDP global session id (see [2],
field). The t= line may be altered to indicate the actual start or stop section 6, o= field). The t= line may be altered to indicate the
time, however. The Gateway might add an i= line to the session actual start or stop time, however. The Gateway might add an i= line
description to indicate such information as how many fax pages were to the session description to indicate such information as how many
sent. The Gateway SHOULD include an Expires: header indicating how long fax pages were sent. The Gateway SHOULD include an Expires: header
it is willing to maintain the monitoring session. If this is indicating how long it is willing to maintain the monitoring session.
unacceptable to the PINT Requestor, then it can close the session by If this is unacceptable to the PINT Requestor, then it can close the
sending an immediate UNSUBSCRIBE message (see 3.5.3.3). session by sending an immediate UNSUBSCRIBE message (see 3.5.3.3).
In principle, a user might send a SUBSCRIBE request after the telephone In principle, a user might send a SUBSCRIBE request after the
network service has completed. This allows, for example, checking up telephone network service has completed. This allows, for example,
"the morning after" to see if the fax was successfully transmitted. checking up "the morning after" to see if the fax was successfully
However, a PINT gateway is only required to keep state about a call for transmitted. However, a PINT gateway is only required to keep state
as long as it indicated previously in an Expires: header sent within the about a call for as long as it indicated previously in an Expires:
response to the original INVITE message that triggered the service header sent within the response to the original INVITE message that
session, within the response to the SUBSCRIBE message, within the triggered the service session, within the response to the SUBSCRIBE
response to any UNSUBSCRIBE message, or within its own UNSUBSCRIBE message, within the response to any UNSUBSCRIBE message, or within
message (but see section 3.5.8, point 3). its own UNSUBSCRIBE message (but see section 3.5.8, point 3).
If the Server no longer has a record of the session to which a Requestor If the Server no longer has a record of the session to which a
has SUBSCRIBEd, it returns "606 Not Acceptable", along with the Requestor has SUBSCRIBEd, it returns "606 Not Acceptable", along with
appropriate Warning: 307 header indicating that the SDP session ID is no the appropriate Warning: 307 header indicating that the SDP session
longer valid. This means that a requesting Client that knows that it ID is no longer valid. This means that a requesting Client that knows
will want information about the status of a session after the session that it will want information about the status of a session after the
terminates SHOULD send a SUBSCRIBE request before the session session terminates SHOULD send a SUBSCRIBE request before the session
terminates. terminates.
3.5.3.2. Sending Status Indications with a NOTIFY request 3.5.3.2. Sending Status Indications with a NOTIFY request
During the subscription period, the Gateway may, from time to time, send During the subscription period, the Gateway may, from time to time,
a spontaneous NOTIFY request to the entity indicated in the Contact: send a spontaneous NOTIFY request to the entity indicated in the
header of the "opening" SUBSCRIBE request. Normally this will happen as Contact: header of the "opening" SUBSCRIBE request. Normally this
a result of any change in the status of the service session for which will happen as a result of any change in the status of the service
the Requestor has subscribed. session for which the Requestor has subscribed.
The receiving user agent server MUST acknowledge this by returning a The receiving user agent server MUST acknowledge this by returning a
final response (normally a "200 OK"). In this version of the PINT final response (normally a "200 OK"). In this version of the PINT
extensions, the Gateway is not required to support redirects (3xx extensions, the Gateway is not required to support redirects (3xx
codes), and so may treat them as a failure. codes), and so may treat them as a failure.
Thus, if the response code class is above 2xx then this may be treated Thus, if the response code class is above 2xx then this may be
by the Gateway as a failure of the monitoring session, and in that treated by the Gateway as a failure of the monitoring session, and in
situation it will immediately attempt to close the session (see next). that situation it will immediately attempt to close the session (see
next).
The NOTIFY request contains the modified session description. For The NOTIFY request contains the modified session description. For
example, the Gateway may be able to indicate a more accurate start or example, the Gateway may be able to indicate a more accurate start or
stop time. stop time.
The Gateway may include a Warning: header to describe some problem with The Gateway may include a Warning: header to describe some problem
the invocation of the service, and may indicate within an i= line some with the invocation of the service, and may indicate within an i=
information about the telephone network session itself. line some information about the telephone network session itself.
Example: Example:
NOTIFY sip:petrack@pager.com SIP/2.0 NOTIFY sip:petrack@pager.com SIP/2.0
To: sip:petrack@pager.com To: sip:petrack@pager.com
From: sip:R2F.pint.com@service.com From: sip:R2F.pint.com@service.com
Call-ID: 19971205T234505.56.78@pager.com Call-ID: 19971205T234505.56.78@pager.com
CSeq: 4711 SUBSCRIBE CSeq: 4711 SUBSCRIBE
Warning: xxx fax aborted, will try for the next hour. Warning: xxx fax aborted, will try for the next hour.
Content-Type:application/sdp Content-Type:application/sdp
c=... c=...
i=3 pages of 5 sent i=3 pages of 5 sent
t=... t=...
3.5.3.3. Closing a monitoring session with an UNSUBSCRIBE request 3.5.3.3. Closing a monitoring session with an UNSUBSCRIBE request
At some point, either the Client's representative User Agent Server or At some point, either the Client's representative User Agent Server
the Gateway may decide to terminate the monitoring session. This is or the Gateway may decide to terminate the monitoring session. This
achieved by sending an UNSUBSCRIBE request to the correspondent server. is achieved by sending an UNSUBSCRIBE request to the correspondent
Such a request indicates that the sender intends to close the monitoring server. Such a request indicates that the sender intends to close
session immediately, and, on receipt of the final response from the the monitoring session immediately, and, on receipt of the final
receiving server, the session is deemed over. response from the receiving server, the session is deemed over.
Note that unlike the SUBSCRIBE request, which is never sent by a PINT Note that unlike the SUBSCRIBE request, which is never sent by a PINT
gateway, an UNSUBSCRIBE request can be sent by a PINT gateway to the gateway, an UNSUBSCRIBE request can be sent by a PINT gateway to the
User Agent Server to indicate that the monitoring session is closed. User Agent Server to indicate that the monitoring session is closed.
(This is analogous to the fact that a gateway never sends an INVITE, (This is analogous to the fact that a gateway never sends an INVITE,
although it can send a BYE to indicate that a telephone call has ended.) although it can send a BYE to indicate that a telephone call has
ended.)
If the Gateway initiates closure of the monitoring session by sending an If the Gateway initiates closure of the monitoring session by sending
UNSUBSCRIBE message, it SHOULD include an "Expires:" header showing for an UNSUBSCRIBE message, it SHOULD include an "Expires:" header
how much longer after this monitoring session is closed it is willing to showing for how much longer after this monitoring session is closed
store information on the service session. This acts as a minimum time it is willing to store information on the service session. This acts
within which the Client can send a new SUBSCRIBE message to open another as a minimum time within which the Client can send a new SUBSCRIBE
monitoring session; after the time indicated in the Expires: header the message to open another monitoring session; after the time indicated
Gateway is free to dispose of any record of the service session, so that in the Expires: header the Gateway is free to dispose of any record
subsequent SUBSCRIBE requests can be rejected with a "606" response. of the service session, so that subsequent SUBSCRIBE requests can be
rejected with a "606" response.
If the subscription period specified by the Client has expired, then the If the subscription period specified by the Client has expired, then
Gateway may send an immediate UNSUBSCRIBE request to the Client's the Gateway may send an immediate UNSUBSCRIBE request to the Client's
representative User Agent Server. This ensures that the monitoring representative User Agent Server. This ensures that the monitoring
session always completes with a UNSUBSCRIBE/response exchange, and that session always completes with a UNSUBSCRIBE/response exchange, and
the representative User Agent Server can avoid maintaining state in that the representative User Agent Server can avoid maintaining state
certain circumstances. in certain circumstances.
3.5.3.4. Timing of SUBSCRIBE requests 3.5.3.4. Timing of SUBSCRIBE requests
As it relies on the Gateway having a copy of the INVITEd session As it relies on the Gateway having a copy of the INVITEd session
description, the SUBSCRIBE message is limited in when it can be issued. description, the SUBSCRIBE message is limited in when it can be
The Gateway must have received the service request to which this issued. The Gateway must have received the service request to which
monitoring session is to be associated, which from the Client's this monitoring session is to be associated, which from the Client's
perspective happens as soon as the Gateway has sent a 1xx response back perspective happens as soon as the Gateway has sent a 1xx response
to it. back to it.
However, once this has been done, there is no reason why the Client However, once this has been done, there is no reason why the Client
should not send a monitoring request. It does not have to wait for the should not send a monitoring request. It does not have to wait for
final response from the Gateway, and it can certainly send the SUBSCRIBE the final response from the Gateway, and it can certainly send the
request before sending the ACK for the Service request final response. SUBSCRIBE request before sending the ACK for the Service request
Beyond this point, the Client is free to send a SUBSCRIBE request when final response. Beyond this point, the Client is free to send a
it decides, unless the Gateway's final response to the initial service SUBSCRIBE request when it decides, unless the Gateway's final
request indicated a short Expires: time. response to the initial service request indicated a short Expires:
time.
However, there are good reasons (see 6.4) why it may be appropriate to However, there are good reasons (see 6.4) why it may be appropriate
start a monitoring session immediately before the service is confirmed to start a monitoring session immediately before the service is
by the PINT Client sending an ACK. At this point the Gateway will have confirmed by the PINT Client sending an ACK. At this point the
decided whether or not it can handle the service request, but will not Gateway will have decided whether or not it can handle the service
have passed the request on to the Executive System. It is therefore in a request, but will not have passed the request on to the Executive
good position to ask the Executive System to enable monitoring when it System. It is therefore in a good position to ask the Executive
sends the service request onwards. In practical implementations, it is System to enable monitoring when it sends the service request
likely that more information on transient service status will be onwards. In practical implementations, it is likely that more
available if this is indicated as being important BEFORE or AS the information on transient service status will be available if this is
service execution phase starts; once execution has begun the level of indicated as being important BEFORE or AS the service execution phase
information that can be returned may be difficult to change. starts; once execution has begun the level of information that can be
returned may be difficult to change.
Thus, whilst it is free to send a SUBSCRIBE request at any point after Thus, whilst it is free to send a SUBSCRIBE request at any point
receiving an Interim response from the Gateway to its service request, after receiving an Interim response from the Gateway to its service
it is recommended that the Client should send such a monitoring request request, it is recommended that the Client should send such a
immediately prior to sending an ACK message confirming the service if it monitoring request immediately prior to sending an ACK message
is interested in transient service status messages. confirming the service if it is interested in transient service
status messages.
3.5.4. The "Require:" header for PINT 3.5.4. The "Require:" header for PINT
PINT clients use the Require: header to signal to the PINT server that a PINT clients use the Require: header to signal to the PINT server
certain PINT extension of SIP is required. PINT 1.0 defines two strings that a certain PINT extension of SIP is required. PINT 1.0 defines
that can go into the Require header: two strings that can go into the Require header:
org.ietf.sip.subscribe -- the server can fulfill SUBSCRIBE requests org.ietf.sip.subscribe -- the server can fulfill SUBSCRIBE requests
and associated methods (see section 3.5.3) and associated methods (see section 3.5.3)
org.ietf.sdp.require -- the PINT server (or the SDP parser associated org.ietf.sdp.require -- the PINT server (or the SDP parser
to it) understands the "require" attribute associated to it) understands the "require"
defined in (section 3.4.4) attribute defined in (section 3.4.4)
Example: Example:
Require:org.ietf.sip.subscribe,org.ietf.sdp.require Require:org.ietf.sip.subscribe,org.ietf.sdp.require
A client SHOULD only include a Require: header where it truly requires A client SHOULD only include a Require: header where it truly
the server to reject the request if the option is not supported. requires the server to reject the request if the option is not
supported.
3.5.5. PINT URLs within PINT requests 3.5.5. PINT URLs within PINT requests
Normally the hostnames and domain names that appear in the PINT URLs are Normally the hostnames and domain names that appear in the PINT URLs
the internal affair of each individual PINT system. A client uses the are the internal affair of each individual PINT system. A client uses
appropriate SDP payload to indicate the particular service it wishes to the appropriate SDP payload to indicate the particular service it
invoke; it is not necessary to use a particular URL to identify the wishes to invoke; it is not necessary to use a particular URL to
service. identify the service.
A PINT URL is used in two different ways within PINT requests: within A PINT URL is used in two different ways within PINT requests: within
the Request-URI, and within the To: and From: headers. Use within the the Request-URI, and within the To: and From: headers. Use within the
Request-URI requires clarification in order to ensure smooth Request-URI requires clarification in order to ensure smooth
interworking with the Telephone Network serviced by the PINT interworking with the Telephone Network serviced by the PINT
infrastructure, and this is covered next. infrastructure, and this is covered next.
3.5.5.1. PINT URLS within Request-URIs 3.5.5.1. PINT URLS within Request-URIs
There are some occasions when it may be useful to indicate service There are some occasions when it may be useful to indicate service
information within the URL in a standardized way: information within the URL in a standardized way:
a. it may not be possible to use SDP information to route the request
if it is encrypted;
b. it allows implementation that make use of I.N. "service
indicators";
c. It enables multiple competing PINT gateways to REGISTER with a
single "broker" server (proxy or redirect) (see section 6.3)
For these reasons, the following conventions for URLs are offered for a. it may not be possible to use SDP information to route the
use in PINT requests: request if it is encrypted;
b. it allows implementation that make use of I.N. "service
indicators";
c. It enables multiple competing PINT gateways to REGISTER with a
single "broker" server (proxy or redirect) (see section 6.3)
1. The user portion of a sip URL indicates the service to be requested. For these reasons, the following conventions for URLs are offered for
At present the following services are defined: use in PINT requests:
R2C (for Request-to-Call) 1. The user portion of a sip URL indicates the service to be
R2F (for Request-to-Fax) requested. At present the following services are defined:
R2HC (for Request-to-Hear-Content)
The user portions "R2C", "R2F", and "R2HC" are reserved for the PINT R2C (for Request-to-Call)
milestone services. Other user portions MUST be used in case the R2F (for Request-to-Fax)
requested service is not one of the Milestone services. See section 6.2 R2HC (for Request-to-Hear-Content)
for some related considerations concerning registrations by competing
PINT systems to a single PINT proxy server acting as a service broker.
2. The host portion of a sip URL contains the domain name of the PINT The user portions "R2C", "R2F", and "R2HC" are reserved for the PINT
service provider. milestone services. Other user portions MUST be used in case the
requested service is not one of the Milestone services. See section
6.2 for some related considerations concerning registrations by
competing PINT systems to a single PINT proxy server acting as a
service broker.
3. A new url-parameter is defined to be "tsp" (for "telephone service 2. The host portion of a sip URL contains the domain name of the PINT
provider"). This can be used to indicate the actual telephone network service provider.
provider to be used to fulfil the PINT request.
Thus, for example:- 3. A new url-parameter is defined to be "tsp" (for "telephone service
INVITE sip:R2C@pint.pintservice.com SIP/2.0 provider"). This can be used to indicate the actual telephone network
INVITE sip:R2F@pint.pintservice.com;tsp=telco.com SIP/2.0 provider to be used to fulfill the PINT request.
INVITE sip:R2HC@pint.mycom.com;tsp=pbx23.mycom.com SIP/2.0
INVITE sip:13@pint.telco.com SIP/2.0 Thus, for example:-
INVITE sip:R2C@pint.pintservice.com SIP/2.0
INVITE sip:R2F@pint.pintservice.com;tsp=telco.com SIP/2.0
INVITE sip:R2HC@pint.mycom.com;tsp=pbx23.mycom.com SIP/2.0
INVITE sip:13@pint.telco.com SIP/2.0
3.5.6. Telephony Network Parameters within PINT URLs 3.5.6. Telephony Network Parameters within PINT URLs
Any legal SIP URL can appear as a PINT URL within the Request-URI or To: Any legal SIP URL can appear as a PINT URL within the Request-URI or
header of a PINT request. But if the address is a telephone address, we To: header of a PINT request. But if the address is a telephone
indicated in section 3.4.3 that it may be necessary to include more address, we indicated in section 3.4.3 that it may be necessary to
information in order correctly to identify the remote telephone terminal include more information in order correctly to identify the remote
or service. PINT clients MAY include these attribute tags within PINT telephone terminal or service. PINT clients MAY include these
URLs if they are necessary or a useful complement to the telephone attribute tags within PINT URLs if they are necessary or a useful
number within the SIP URL. These attribute tags MUST be included as URL complement to the telephone number within the SIP URL. These
parameters as defined in [1] (i.e. in the semi-colon separated manner). attribute tags MUST be included as URL parameters as defined in [1]
(i.e. in the semi-colon separated manner).
The following is an example of a PINT URL containing extra attribute The following is an example of a PINT URL containing extra attribute
tags: tags:
sip:+9725228808@pint.br.com;user=phone;require=Q763-plan;a=Q763-plan:4 sip:+9725228808@pint.br.com;user=phone;require=Q763-plan;a=Q763-plan:4
As we noted in section 3.4.3, these extra attribute parameters will not As we noted in section 3.4.3, these extra attribute parameters will
normally be needed within a URL, because there is a great deal of not normally be needed within a URL, because there is a great deal of
context available to the help the server interpret the phone number context available to help the server interpret the phone number
correctly. In particular, there is the SIP URL within the To: header, correctly. In particular, there is the SIP URL within the To: header,
and there is also the Request-URI. In most cases this provides and there is also the Request-URI. In most cases this provides
sufficient information for the telephone network. sufficient information for the telephone network.
The SDP attributes defined in section 3 above will normally only be used The SDP attributes defined in section 3 above will normally only be
when they are needed to supply necessary context to identify a telephone used when they are needed to supply necessary context to identify a
terminal. telephone terminal.
3.5.7. REGISTER requests within PINT 3.5.7. REGISTER requests within PINT
A PINT gateway is a SIP user agent server. A User Agent Server uses the A PINT gateway is a SIP user agent server. A User Agent Server uses
REGISTER request to tell a proxy or redirect server that it is available the REGISTER request to tell a proxy or redirect server that it is
to "receive calls" (i.e. to service requests). Thus a PINT Gateway available to "receive calls" (i.e. to service requests). Thus a PINT
registers with a proxy or redirect server the service that is accessible Gateway registers with a proxy or redirect server the service that is
via itself, whilst in SIP, a user is registering his/her presence at a accessible via itself, whilst in SIP, a user is registering his/her
particular SIP Server. presence at a particular SIP Server.
There may be competing PINT servers that can offer the same PINT service There may be competing PINT servers that can offer the same PINT
trying to register at a single PINT server. The PINT server might act as service trying to register at a single PINT server. The PINT server
a "broker" among the various PINT gateways that can fulfil a request. A might act as a "broker" among the various PINT gateways that can
format for PINT URLs was specified in section 3.5.5 that enables fulfill a request. A format for PINT URLs was specified in section
independent PINT systems to REGISTER an offer to provide the same 3.5.5 that enables independent PINT systems to REGISTER an offer to
service. The registrar can apply its own mechanisms and policies to provide the same service. The registrar can apply its own mechanisms
decide how to respond to INVITEs from clients seeking service (See and policies to decide how to respond to INVITEs from clients seeking
section 6.3 for some possible deployment options). There is no change service (See section 6.3 for some possible deployment options). There
between SIP and PINT REGISTER semantics or syntax. is no change between SIP and PINT REGISTER semantics or syntax.
Of course, the information in the PINT URLs within the REGISTER request Of course, the information in the PINT URLs within the REGISTER
may not be sufficient to completely define the service that a gateway request may not be sufficient to completely define the service that a
can offer. The use of SIP and SDP within PINT REGISTER requests to gateway can offer. The use of SIP and SDP within PINT REGISTER
enable a gateway to specify in more detail the services it can offer is requests to enable a gateway to specify in more detail the services
the subject of future study. it can offer is the subject of future study.
3.5.8. BYE Requests in PINT 3.5.8. BYE Requests in PINT
The semantics of BYE requests within PINT requires some extra precision. The semantics of BYE requests within PINT requires some extra
One issue concerns conferences that "cannot be left", and the other precision. One issue concerns conferences that "cannot be left", and
concerns keeping call state after the BYE. the other concerns keeping call state after the BYE.
The BYE request [1] is normally used to indicate that the originating The BYE request [1] is normally used to indicate that the originating
entity no longer wishes to be involved in the specified call. The entity no longer wishes to be involved in the specified call. The
request terminates the call and the media session. Applying this model request terminates the call and the media session. Applying this
to PINT, if a PINT client makes a request that results in invocation of model to PINT, if a PINT client makes a request that results in
a telephone call from A to B, a BYE request from the client, if invocation of a telephone call from A to B, a BYE request from the
accepted, should result in a termination of the phone call. client, if accepted, should result in a termination of the phone
call.
One might expect this to be the case if the telephone call has not One might expect this to be the case if the telephone call has not
started when the BYE request is received. For example, if a request to started when the BYE request is received. For example, if a request
fax is sent with a t= line indicating that the fax is to be sent to fax is sent with a t= line indicating that the fax is to be sent
tomorrow at 4 AM, the requestor might wish to cancel the request before tomorrow at 4 AM, the requestor might wish to cancel the request
the specified time. before the specified time.
However, even if the call has yet to start, it may not be possible to However, even if the call has yet to start, it may not be possible to
terminate the media session on the telephone system side. For example, terminate the media session on the telephone system side. For
the fax call may be in progress when the BYE arrives, and perhaps it is example, the fax call may be in progress when the BYE arrives, and
just not possible to cancel the fax in session. Another possibility is perhaps it is just not possible to cancel the fax in session. Another
that the entire telephone-side service might be completed before the BYE possibility is that the entire telephone-side service might be
is received. In the above Request-to-Fax example, the BYE might be sent completed before the BYE is received. In the above Request-to-Fax
the following morning, and the entire fax has been sent before the BYE example, the BYE might be sent the following morning, and the entire
was received. It is too late to send the BYE. fax has been sent before the BYE was received. It is too late to send
the BYE.
In the case where the telephone network cannot terminate the call, the In the case where the telephone network cannot terminate the call,
server MUST return a "606 Not Acceptable" response to the BYE, along the server MUST return a "606 Not Acceptable" response to the BYE,
with a session description that indicates the telephone network session along with a session description that indicates the telephone network
that is causing the problem. session that is causing the problem.
Thus, in PINT, a "Not Acceptable" response MAY be returned both to Thus, in PINT, a "Not Acceptable" response MAY be returned both to
INVITE and BYE requests. It indicates that some aspect of the session INVITE and BYE requests. It indicates that some aspect of the session
description makes the request unacceptable. description makes the request unacceptable.
By allowing a server to return a "Not Acceptable" response to BYE By allowing a server to return a "Not Acceptable" response to BYE
requests, we are not changing its semantics, just enlarging its use. requests, we are not changing its semantics, just enlarging its use.
A combination of Warning: headers and i= lines within the session A combination of Warning: headers and i= lines within the session
description can be used to indicate the precise nature of the problem. description can be used to indicate the precise nature of the
problem.
Example: Example:
SIP/2.0 606 Not Acceptable SIP/2.0 606 Not Acceptable
From: ... From: ...
To: ....... To: .......
..... .....
Warning: 399 pint.mycom.com Fax in progress, service cannot be Warning: 399 pint.mycom.com Fax in progress, service cannot be
aborted aborted
Content-Type: application/sdp Content-Type: application/sdp
Content-Length: ... Content-Length: ...
v=0 v=0
... ...
... ...
i=3 of 5 pages sent OK i=3 of 5 pages sent OK
c=TN RFC2543 +12014064090 c=TN RFC2543 +12014064090
m=image 1 fax tif m=image 1 fax tif
a=fmtp:tif uri:http://tifsRus.com/yyyyyy.tif a=fmtp:tif uri:http://tifsRus.com/yyyyyy.tif
Note that the server might return an updated session description within Note that the server might return an updated session description
a successful response to a BYE as well. This can be used, for example, within a successful response to a BYE as well. This can be used, for
to indicate the actual start times and stop times of the telephone example, to indicate the actual start times and stop times of the
session, or how many pages were sent in the fax transmission. telephone session, or how many pages were sent in the fax
transmission.
The second issue concerns how long must a server keep call state after The second issue concerns how long must a server keep call state
receiving a BYE. A question arises because other clients might still after receiving a BYE. A question arises because other clients might
wish to send queries about the telephone network session that was the still wish to send queries about the telephone network session that
subject of the PINT transaction. Ordinary SIP semantics have three was the subject of the PINT transaction. Ordinary SIP semantics have
important implications for this situation: three important implications for this situation:
1. A BYE indicates that the requesting client will clear out all call 1. A BYE indicates that the requesting client will clear out all call
state as soon as it receives a successful response. A client SHOULD NOT state as soon as it receives a successful response. A client SHOULD
send a SUBSCRIBE request after it has sent a BYE. NOT send a SUBSCRIBE request after it has sent a BYE.
2. A server may return an Expires: header within a successful response 2. A server may return an Expires: header within a successful
to a BYE request. This indicates for how long the server will retain response to a BYE request. This indicates for how long the server
session state about the telephone network session. At any point during will retain session state about the telephone network session. At any
this time, a client may send a SUBSCRIBE request to the server to learn point during this time, a client may send a SUBSCRIBE request to the
about the session state (although as explained in the previous paragraph, server to learn about the session state (although as explained in the
a client that has sent a BYE will not normally send a SUBSCRIBE). previous paragraph, a client that has sent a BYE will not normally
send a SUBSCRIBE).
3. When engaged in a SUBSCRIBE/NOTIFY monitoring session, PINT servers 3. When engaged in a SUBSCRIBE/NOTIFY monitoring session, PINT
that send UNSUBSCRIBE to a URL listed in the Contact: header of a client servers that send UNSUBSCRIBE to a URL listed in the Contact: header
request SHOULD not clear session state until after the successful of a client request SHOULD not clear session state until after the
response to the UNSUBSCRIBE message is received. For example, it may be successful response to the UNSUBSCRIBE message is received. For
that the requesting client host is turned off (or in a low power mode) example, it may be that the requesting client host is turned off (or
when the telephone service is executed (and is therefore not available in a low power mode) when the telephone service is executed (and is
at the location previously specified in the Contact: attribute) to therefore not available at the location previously specified in the
receive the PINT server's UNSUBSCRIBE. Of course, it is possible that Contact: attribute) to receive the PINT server's UNSUBSCRIBE. Of
the UNSUBSCRIBE request will simply time out. course, it is possible that the UNSUBSCRIBE request will simply time
out.
4. Examples of PINT Requests and Responses 4. Examples of PINT Requests and Responses
4.1. A request to a call center from an anonymous user to receive a 4.1. A request to a call center from an anonymous user to receive a
phone call. phone call.
C->S: INVITE sip:R2C@pint.mailorder.com SIP/2.0 C->S: INVITE sip:R2C@pint.mailorder.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:anon-1827631872@chinet.net From: sip:anon-1827631872@chinet.net
To: sip:+1-201-456-7890@iron.org;user=phone To: sip:+1-201-456-7890@iron.org;user=phone
Call-ID: 19971205T234505.56.78@pager.com Call-ID: 19971205T234505.56.78@pager.com
CSeq: 4711 INVITE CSeq: 4711 INVITE
Subject: Sale on Ironing Boards Subject: Sale on Ironing Boards
Content-type: application/sdp Content-type: application/sdp
Content-Length: 174 Content-Length: 174
v=0
o=- 2353687637 2353687637 IN IP4 128.3.4.5
s=R2C
i=Ironing Board Promotion
e=anon-1827631872@chinet.net
t=2353687637 0
m=audio 1 voice -
c=TN RFC2543 +1-201-406-4090
In this example, the context that is required to interpret the To: v=0
address as a telephone number is not given explicitly; it is implicitly o=- 2353687637 2353687637 IN IP4 128.3.4.5
known to the R2C@pint.mailorder.com server. But the telephone of the s=R2C
person who wishes to receive the call is explicitly identified as an i=Ironing Board Promotion
internationally significant E.164 number that falls within the North e=anon-1827631872@chinet.net
American numbering plan (because of the "+1" within the c= line). t=2353687637 0
m=audio 1 voice -
c=TN RFC2543 +1-201-406-4090
In this example, the context that is required to interpret the To:
address as a telephone number is not given explicitly; it is
implicitly known to the R2C@pint.mailorder.com server. But the
telephone of the person who wishes to receive the call is explicitly
identified as an internationally significant E.164 number that falls
within the North American numbering plan (because of the "+1" within
the c= line).
4.2. A request from a non anonymous customer (John Jones) to receive a 4.2. A request from a non anonymous customer (John Jones) to receive a
phone call from a particular sales agent (Mary James) concerning the phone call from a particular sales agent (Mary James) concerning
defective ironing board that was purchased the defective ironing board that was purchased
C->S: INVITE sip:marketing@pint.mailorder.com SIP/2.0 C->S: INVITE sip:marketing@pint.mailorder.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:john.jones.3@chinet.net From: sip:john.jones.3@chinet.net
To: sip:mary.james@mailorder.com To: sip:mary.james@mailorder.com
Call-ID: 19971205T234505.56.78@pager.com Call-ID: 19971205T234505.56.78@pager.com
CSeq: 4712 INVITE CSeq: 4712 INVITE
Subject: Defective Ironing Board - want refund Subject: Defective Ironing Board - want refund
Content-type: application/sdp Content-type: application/sdp
Content-Length: 150 Content-Length: 150
v=0 v=0
o=- 2353687640 2353687640 IN IP4 128.3.4.5 o=- 2353687640 2353687640 IN IP4 128.3.4.5
s=marketing s=marketing
e=john.jones.3@chinet.net e=john.jones.3@chinet.net
c= TN RFC2543 +1-201-406-4090 c= TN RFC2543 +1-201-406-4090
t=2353687640 0 t=2353687640 0
m=audio 1 voice - m=audio 1 voice -
The To: line might include the Mary James's phone number instead of a The To: line might include the Mary James's phone number instead of a
email-like address. An implementation that cannot accept email-like URLs email-like address. An implementation that cannot accept email-like
in the "To:" header must decline the request with a 606 Not Acceptable. URLs in the "To:" header must decline the request with a 606 Not
Note that the sending PINT client "knows" that the PINT Gateway Acceptable. Note that the sending PINT client "knows" that the PINT
contacted with the "marketing@pint.mailorder.com" Request-URI is capable Gateway contacted with the "marketing@pint.mailorder.com" Request-URI
of processing the client request as expected. (see 3.5.5.1 for a is capable of processing the client request as expected. (see 3.5.5.1
discussion on this). for a discussion on this).
Note also that such a telephone call service could be implemented on the Note also that such a telephone call service could be implemented on
phone side with different details. For example, it might be that first the phone side with different details. For example, it might be that
the agent's phone rings, and then the customer's phone rings, or it first the agent's phone rings, and then the customer's phone rings,
might be that first the customer's phone rings and he hears silly music or it might be that first the customer's phone rings and he hears
until the agent comes on line. If necessary, such service parameter silly music until the agent comes on line. If necessary, such service
details might be indicated in "a=" attribute lines within the session parameter details might be indicated in "a=" attribute lines within
description. The specification of such attribute lines for service the session description. The specification of such attribute lines
consistency is beyond the scope of the PINT 1.0 specifications. for service consistency is beyond the scope of the PINT 1.0
specifications.
4.3. A request from the same user to get a fax back on how to assemble 4.3. A request from the same user to get a fax back on how to assemble
the Ironing Board the Ironing Board
C->S: INVITE sip:faxback@pint.mailorder.com SIP/2.0 C->S: INVITE sip:faxback@pint.mailorder.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:john.jones.3@chinet.net From: sip:john.jones.3@chinet.net
To: sip:1-800-3292225K@steam.edu;user=phone;phone-context=+1 To: sip:1-800-3292225@steam.edu;user=phone;phone-context=+1
Call-ID: 19971205T234505.66.79@chinet.net Call-ID: 19971205T234505.66.79@chinet.net
CSeq: 4713 INVITE CSeq: 4713 INVITE
Content-type: application/sdp Content-type: application/sdp
Content-Length: 218 Content-Length: 218
v=0 v=0
o=- 2353687660 2353687660 IN IP4 128.3.4.5 o=- 2353687660 2353687660 IN IP4 128.3.4.5
s=faxback s=faxback
e=john.jones.3@chinet.net e=john.jones.3@chinet.net
t=2353687660 0 t=2353687660 0
m=application 1 fax URI m=application 1 fax URI
c=TN RFC2543 1-201-406-4091 c=TN RFC2543 1-201-406-4091
a=fmtp:URI uri:http://localstore/Products/IroningBoards/2344.html a=fmtp:URI uri:http://localstore/Products/IroningBoards/2344.html
In this example, the fax to be sent is stored on some local server In this example, the fax to be sent is stored on some local server
(localstore), whose name may be only resolvable, or that may only be (localstore), whose name may be only resolvable, or that may only be
reachable, from within the IP network on which the PINT server sits. The reachable, from within the IP network on which the PINT server sits.
phone number to be dialled is a "local phone number" as well. There is The phone number to be dialled is a "local phone number" as well.
no "phone-context" attribute, so the context (in this case, for which There is no "phone-context" attribute, so the context (in this case,
nation the number is "nationally significant") must be supplied by the for which nation the number is "nationally significant") must be
faxback@pint.mailorder.com PINT server. supplied by the faxback@pint.mailorder.com PINT server.
If the server that receives it does not understand the number, it SHOULD If the server that receives it does not understand the number, it
decline the request and include a "Network Address Not Understood" warning. SHOULD decline the request and include a "Network Address Not
Note that no "require" attribute was used here, since it is very likely Understood" warning. Note that no "require" attribute was used here,
that the request can be serviced even by a server that does not support since it is very likely that the request can be serviced even by a
the "require" attribute. server that does not support the "require" attribute.
4.4. A request from same user to have that same information read out 4.4. A request from same user to have that same information read out
over the phone over the phone
C->S: INVITE sip:faxback@pint.mailorder.com SIP/2.0 C->S: INVITE sip:faxback@pint.mailorder.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:john.jones.3@chinet.net From: sip:john.jones.3@chinet.net
To: sip:1-800-3292225@steam.edu;user=phone;phone-context=+1 To: sip:1-800-3292225@steam.edu;user=phone;phone-context=+1
Call-ID: 19971205T234505.66.79@chinet.net Call-ID: 19971205T234505.66.79@chinet.net
CSeq: 4713 INVITE CSeq: 4713 INVITE
Content-type: application/sdp Content-type: application/sdp
Content-Length: 220 Content-Length: 220
v=0 v=0
o=- 2353687660 2353687660 IN IP4 128.3.4.5 o=- 2353687660 2353687660 IN IP4 128.3.4.5
s=faxback s=faxback
e=john.jones.3@chinet.net e=john.jones.3@chinet.net
t=2353687660 0 t=2353687660 0
m=application 1 voice URI m=application 1 voice URI
c=TN RFC2543 1-201-406-4090 c=TN RFC2543 1-201-406-4090
a=fmtp:URI uri:http://localstore/Products/IroningBoards/2344.html a=fmtp:URI uri:http://localstore/Products/IroningBoards/2344.html
4.5. A request to send an included text page to a friend's pager. 4.5. A request to send an included text page to a friend's pager.
In this example, the text to be paged out is included in the request.
In this example, the text to be paged out is included in the request.
C->S: INVITE sip:R2F@pint.pager.com SIP/2.0 C->S: INVITE sip:R2F@pint.pager.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:scott.petrack@chinet.net From: sip:scott.petrack@chinet.net
To: sip:R2F@pint.pager.com To: sip:R2F@pint.pager.com
Call-ID: 19974505.66.79@chinet.net Call-ID: 19974505.66.79@chinet.net
CSeq: 4714 INVITE CSeq: 4714 INVITE
Content-Type: multipart/related; boundary=--next Content-Type: multipart/related; boundary=--next
----next ----next
Content-Type: application/sdp Content-Type: application/sdp
skipping to change at page 36, line 5 skipping to change at page 41, line 5
v=0 v=0
o=- 2353687700 2353687700 IN IP4 128.3.4.5 o=- 2353687700 2353687700 IN IP4 128.3.4.5
s=faxserver s=faxserver
e=scott.petrack@chinet.net e=scott.petrack@chinet.net
t=2353687700 0 t=2353687700 0
m=image 1 fax tif gif m=image 1 fax tif gif
c= TN RFC2543 +972-9-956-1867 c= TN RFC2543 +972-9-956-1867
a=fmtp:tif uri:http://petrack/images/tif/picture1.tif a=fmtp:tif uri:http://petrack/images/tif/picture1.tif
a=fmtp:gif uri:http://petrack/images/gif/picture1.gif a=fmtp:gif uri:http://petrack/images/gif/picture1.gif
The image is available as tif or as gif. The tif is the preferred The image is available as tif or as gif. The tif is the preferred
format. Note that the http server where the pictures reside is local, format. Note that the http server where the pictures reside is local,
and the PINT server is also local (because it can resolve machine name and the PINT server is also local (because it can resolve machine
"petrack") name "petrack")
4.7. A request to read out over the phone two pieces of content in 4.7. A request to read out over the phone two pieces of content in
sequence. sequence.
First some included text is read out by text-to-speech. Then some text
that is stored at some URI on the internet is read out. First some included text is read out by text-to-speech. Then some
text that is stored at some URI on the internet is read out.
C->S: INVITE sip:R2HC@pint.acme.com SIP/2.0 C->S: INVITE sip:R2HC@pint.acme.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
From: sip:scott.petrack@chinet.net From: sip:scott.petrack@chinet.net
To: sip:R2HC@pint.acme.com To: sip:R2HC@pint.acme.com
Call-ID: 19974505.66.79@chinet.net Call-ID: 19974505.66.79@chinet.net
CSeq: 4716 INVITE CSeq: 4716 INVITE
Content-Type: multipart/related; boundary=next Content-Type: multipart/related; boundary=next
--next --next
skipping to change at page 36, line 49 skipping to change at page 42, line 6
Content-Type: text/plain Content-Type: text/plain
Content-ID: 2@53655768 Content-ID: 2@53655768
Content-Length: 172 Content-Length: 172
Hello!! I am about to read out to you the document you Hello!! I am about to read out to you the document you
requested, "uri:http://www.your.com/texts/stuff.doc". requested, "uri:http://www.your.com/texts/stuff.doc".
We hope you like acme.com's new speech synthesis server. We hope you like acme.com's new speech synthesis server.
--next-- --next--
4.8. Request for the prices for ISDN to be sent to my fax machine 4.8. Request for the prices for ISDN to be sent to my fax machine
INVITE sip:R2FB@pint.bt.co.uk SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 INVITE sip:R2FB@pint.bt.co.uk SIP/2.0
To: sip:0345-12347-01@pint.bt.co.uk;user=phone;phone-context=+44 Via: SIP/2.0/UDP 169.130.12.5
From: sip:hank.wangford@newts.demon.co.uk To: sip:0345-12347-01@pint.bt.co.uk;user=phone;phone-context=+44
Call-ID: 19981204T201505.56.78@demon.co.uk From: sip:hank.wangford@newts.demon.co.uk
CSeq: 4716 INVITE Call-ID: 19981204T201505.56.78@demon.co.uk
Subject: Price List CSeq: 4716 INVITE
Content-type: application/sdp Subject: Price List
Content-Length: 169 Content-type: application/sdp
v=0 Content-Length: 169
o=- 2353687740 2353687740 IN IP4 128.3.4.5
s=R2FB v=0
i=ISDN Price List o=- 2353687740 2353687740 IN IP4 128.3.4.5
e=hank.wangford@newts.demon.co.uk s=R2FB
t=2353687740 0 i=ISDN Price List
m=text 1 fax - e=hank.wangford@newts.demon.co.uk
c=TN RFC2543 +44-1794-8331010 t=2353687740 0
m=text 1 fax -
c=TN RFC2543 +44-1794-8331010
4.9. Request for a callback 4.9. Request for a callback
INVITE sip:R2C@pint.bt.co.uk SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5
To: sip:0345-123456@pint.bt.co.uk;user=phone;phone-context=+44
From: sip:hank.wangford@newts.demon.co.uk
Call-ID: 19981204T234505.56.78@demon.co.uk
CSeq: 4717 INVITE
Subject: It costs HOW much?
Content-type: application/sdp
Content-Length: 176
v=0 INVITE sip:R2C@pint.bt.co.uk SIP/2.0
o=- 2353687760 2353687760 IN IP4 128.3.4.5 Via: SIP/2.0/UDP 169.130.12.5
s=R2C To: sip:0345-123456@pint.bt.co.uk;user=phone;phone-context=+44
i=ISDN pre-sales query From: sip:hank.wangford@newts.demon.co.uk
e=hank.wangford@newts.demon.co.uk Call-ID: 19981204T234505.56.78@demon.co.uk
c=TN RFC2543 +44-1794-8331013 CSeq: 4717 INVITE
t=2353687760 0 Subject: It costs HOW much?
m=audio 1 voice - Content-type: application/sdp
Content-Length: 176
4.10.Sending a set of information in response to an enquiry v=0
o=- 2353687760 2353687760 IN IP4 128.3.4.5
s=R2C
i=ISDN pre-sales query
e=hank.wangford@newts.demon.co.uk
c=TN RFC2543 +44-1794-8331013
t=2353687760 0
m=audio 1 voice -
INVITE sip:R2FB@pint.bt.co.uk SIP/2.0 4.10. Sending a set of information in response to an enquiry
Via: SIP/2.0/UDP 169.130.12.5
To: sip:0345-12347-01@pint.bt.co.uk;user=phone;phone-context=+44
From: sip:colin.masterton@sales.hh.bt.co.uk
Call-ID: 19981205T234505.56.78@sales.hh.bt.co.uk
CSeq: 1147 INVITE
Subject: Price Info, as requested
Content-Type: multipart/related; boundary=next
--next INVITE sip:R2FB@pint.bt.co.uk SIP/2.0
Content-type: application/sdp Via: SIP/2.0/UDP 169.130.12.5
Content-Length: 325 To: sip:0345-12347-01@pint.bt.co.uk;user=phone;phone-context=+44
v=0 From: sip:colin.masterton@sales.hh.bt.co.uk
o=- 2353687780 2353687780 IN IP4 128.3.4.5 Call-ID: 19981205T234505.56.78@sales.hh.bt.co.uk
s=R2FB CSeq: 1147 INVITE
i=Your documents Subject: Price Info, as requested
e=colin.masterton@sales.hh.bt.co.uk Content-Type: multipart/related; boundary=next
t=2353687780 0
m=application 1 fax octet-stream
c=TN RFC2543 +44-1794-8331010
a=fmtp:octet-stream uri:http://www.bt.co.uk/imgs/pipr.gif opr:
spr:2@53655768
--next --next
Content-Type: text/plain Content-type: application/sdp
Content-ID: 2@53655768 Content-Length: 325
Content-Length: 352 v=0
o=- 2353687780 2353687780 IN IP4 128.3.4.5
s=R2FB
i=Your documents
e=colin.masterton@sales.hh.bt.co.uk
t=2353687780 0
m=application 1 fax octet-stream
c=TN RFC2543 +44-1794-8331010
a=fmtp:octet-stream uri:http://www.bt.co.uk/imgs/pipr.gif opr:
spr:2@53655768
Dear Sir, --next
Thank you for your enquiry. I have checked availability in your Content-Type: text/plain
area, and we can provide service to your cottage. I enclose a Content-ID: 2@53655768
quote for the costs of installation, together with the ongoing Content-Length: 352
rental costs for the line. If you want to proceed with this,
please quote job reference isdn/hh/123.45.9901.
Yours Sincerely,
Colin Masterton
--next--
Note that the "implicit" faxback content is given by an EMPTY opaque Dear Sir,
reference in the middle of the fmtp line in this example. Thank you for your enquiry. I have checked availability in your
area, and we can provide service to your cottage. I enclose a
quote for the costs of installation, together with the ongoing
rental costs for the line. If you want to proceed with this,
please quote job reference isdn/hh/123.45.9901.
Yours Sincerely,
Colin Masterton
--next--
4.11.Sportsline "headlines" message sent to your phone/pager/fax Note that the "implicit" faxback content is given by an EMPTY opaque
(i) phone reference in the middle of the fmtp line in this example.
INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5
To:
sip:1-900-123-456-7@wwos.skynet.com;user=phone;phone-context=+1
From: sip:fred.football.fan@skynet.com
Call-ID: 19971205T234505.56.78@chinet.net
CSeq: 4721 INVITE
Subject: Wonderful World Of Sports NFL Final Scores
Content-type: application/sdp
Content-Length: 220
v=0 4.11. Sportsline "headlines" message sent to your phone/pager/fax
o=- 2353687800 2353687800 IN IP4 128.3.4.5
s=R2FB
i=NFL Final Scores
e=fred.football.fan@skynet.com
c=TN RFC2543 +44-1794-8331013
t=2353687800 0
m=audio 1 voice x-pay
a=fmtp:x-pay opr:mci.com/md5:<crypto signature>
(ii) fax (i) phone
INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0 INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
To: sip:1-900-123-456-7@wwos.skynet.com;user=phone; To:
phone-context=+1 sip:1-900-123-456-7@wwos.skynet.com;user=phone;phone-context=+1
From: sip:fred.football.fan@skynet.com From: sip:fred.football.fan@skynet.com
Call-ID: 19971205T234505.56.78@chinet.net Call-ID: 19971205T234505.56.78@chinet.net
CSeq: 4722 INVITE CSeq: 4721 INVITE
Subject: Wonderful World Of Sports NFL Final Scores Subject: Wonderful World Of Sports NFL Final Scores
Content-type: application/sdp Content-type: application/sdp
Content-Length: 217 Content-Length: 220
v=0
o=- 2353687820 2353687820 IN IP4 128.3.4.5
s=R2FB
i=NFL Final Scores
e=fred.football.fan@skynet.com
c=TN RFC2543 +44-1794-8331010
t=2353687820 0
m=text 1 fax x-pay
a=fmtp:x-pay opr:mci.com/md5:<crypto signature>
(iii) pager v=0
INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0 o=- 2353687800 2353687800 IN IP4 128.3.4.5
Via: SIP/2.0/UDP 169.130.12.5 s=R2FB
To: sip:1-900-123-456-7@wwos.skynet.com;user=phone; i=NFL Final Scores
phone-context=+1 e=fred.football.fan@skynet.com
From: sip:fred.football.fan@skynet.com c=TN RFC2543 +44-1794-8331013
Call-ID: 19971205T234505.56.78@chinet.net t=2353687800 0
CSeq: 4723 INVITE m=audio 1 voice x-pay
Subject: Wonderful World Of Sports NFL Final Scores a=fmtp:x-pay opr:mci.com/md5:<crypto signature>
Content-type: application/sdp
Content-Length: 219
v=0 (ii) fax
o=- 2353687840 2353687840 IN IP4 128.3.4.5 INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0
s=R2FB Via: SIP/2.0/UDP 169.130.12.5
i=NFL Final Scores To: sip:1-900-123-456-7@wwos.skynet.com;user=phone;
e=fred.football.fan@skynet.com phone-context=+1
c=TN RFC2543 +44-1794-8331015 From: sip:fred.football.fan@skynet.com
t=2353687840 0 Call-ID: 19971205T234505.56.78@chinet.net
m=text 1 pager x-pay CSeq: 4722 INVITE
a=fmtp:x-pay opr:mci.com/md5:<crypto signature> Subject: Wonderful World Of Sports NFL Final Scores
Content-type: application/sdp
Content-Length: 217
Note that these are all VERY similar. v=0
o=- 2353687820 2353687820 IN IP4 128.3.4.5
s=R2FB
i=NFL Final Scores
e=fred.football.fan@skynet.com
c=TN RFC2543 +44-1794-8331010
t=2353687820 0
m=text 1 fax x-pay
a=fmtp:x-pay opr:mci.com/md5:<crypto signature>
4.12.Automatically giving someone a fax copy of your phone bill (iii) pager
INVITE sip:R2FB@pint.wwos.skynet.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5
To: sip:1-900-123-456-7@wwos.skynet.com;user=phone;
phone-context=+1
From: sip:fred.football.fan@skynet.com
Call-ID: 19971205T234505.56.78@chinet.net
CSeq: 4723 INVITE
Subject: Wonderful World Of Sports NFL Final Scores
Content-type: application/sdp
Content-Length: 219
v=0
o=- 2353687840 2353687840 IN IP4 128.3.4.5
s=R2FB
i=NFL Final Scores
e=fred.football.fan@skynet.com
c=TN RFC2543 +44-1794-8331015
t=2353687840 0
m=text 1 pager x-pay
a=fmtp:x-pay opr:mci.com/md5:<crypto signature>
Note that these are all VERY similar.
4.12. Automatically giving someone a fax copy of your phone bill
INVITE sip:BillsRUs@pint.sprint.com SIP/2.0 INVITE sip:BillsRUs@pint.sprint.com SIP/2.0
Via: SIP/2.0/UDP 169.130.12.5 Via: SIP/2.0/UDP 169.130.12.5
To: sip:+1-555-888-1234@fbi.gov;user=phone To: sip:+1-555-888-1234@fbi.gov;user=phone
From: sip:agent.mulder@fbi.gov From: sip:agent.mulder@fbi.gov
Call-ID: 19991231T234505.56.78@fbi.gov Call-ID: 19991231T234505.56.78@fbi.gov
CSeq: 911 INVITE CSeq: 911 INVITE
Subject: Itemised Bill for January 98 Subject: Itemised Bill for January 98
Content-type: application/sdp Content-type: application/sdp
Content-Length: 247 Content-Length: 247
skipping to change at page 40, line 14 skipping to change at page 46, line 5
v=0 v=0
o=- 2353687860 2353687860 IN IP4 128.3.4.5 o=- 2353687860 2353687860 IN IP4 128.3.4.5
s=BillsRUs s=BillsRUs
i=Joe Pendleton's Phone Bill i=Joe Pendleton's Phone Bill
e=agent.mulder@fbi.gov e=agent.mulder@fbi.gov
c=TN RFC2543 +1-202-833-1010 c=TN RFC2543 +1-202-833-1010
t=2353687860 0 t=2353687860 0
m=text 1 fax x-files-id m=text 1 fax x-files-id
a=fmtp:x-files-id opr:fbi.gov/jdcn-123@45:3des;base64,<signature> a=fmtp:x-files-id opr:fbi.gov/jdcn-123@45:3des;base64,<signature>
Note: in this case the opaque reference is a collection of data used to Note: in this case the opaque reference is a collection of data used
convince the Executive System that the requester has the right to get to convince the Executive System that the requester has the right to
this information, rather than selecting the particular content (the A get this information, rather than selecting the particular content
party in the To: field of the SIP "wrapper" does that alone). (the A party in the To: field of the SIP "wrapper" does that alone).
5. Security Considerations 5. Security Considerations
5.1. Basic Principles for PINT Use 5.1. Basic Principles for PINT Use
A PINT Gateway, and the Executive System(s) with which that Gateway is A PINT Gateway, and the Executive System(s) with which that Gateway
associated, exist to provide service to PINT Requestors. The aim of the is associated, exist to provide service to PINT Requestors. The aim
PINT protocol is to pass requests from those users on to a PINT Gateway of the PINT protocol is to pass requests from those users on to a
so an associated Executive System can service those requests. PINT Gateway so an associated Executive System can service those
requests.
5.1.1. Responsibility for service requests 5.1.1. Responsibility for service requests
The facility of making a GSTN-based call to numbers specified in the The facility of making a GSTN-based call to numbers specified in the
PINT request, however, comes with some risks. The request can specify an PINT request, however, comes with some risks. The request can specify
incorrect telephone of fax number. It is also possible that the an incorrect telephone of fax number. It is also possible that the
Requestor has purposely entered the telephone number of an innocent Requestor has purposely entered the telephone number of an innocent
third party. Finally, the request may have been intercepted on its way third party. Finally, the request may have been intercepted on its
through any intervening PINT or SIP infrastructure, and the request may way through any intervening PINT or SIP infrastructure, and the
have been altered. request may have been altered.
In any of these cases, the result may be that a call is placed In any of these cases, the result may be that a call is placed
incorrectly. Where there is intent or negligence, this may be construed incorrectly. Where there is intent or negligence, this may be
as harrasment of the person incorrectly receiving the call. Whilst the construed as harassment of the person incorrectly receiving the call.
regulatory framework for misuse of Internet connections differs Whilst the regulatory framework for misuse of Internet connections
throughout the world and is not always mature, the rules under which differs throughout the world and is not always mature, the rules
GSTN calls are made are much more settled. Someone may be liable for under which GSTN calls are made are much more settled. Someone may be
mistaken or incorrect calls. liable for mistaken or incorrect calls.
Understandably, the GSTN Operators would prefer that this someone is not Understandably, the GSTN Operators would prefer that this someone is
them, so they will need to ensure that any PINT Gateway and Executive not them, so they will need to ensure that any PINT Gateway and
System combination does not generate incorrect calls through some error Executive System combination does not generate incorrect calls
in the Gateway or Executive system implementation or GSTN-internal through some error in the Gateway or Executive system implementation
communications fault. Equally, it is important that the Operator can or GSTN-internal communications fault. Equally, it is important that
show that they act only on requests that they have good reason to the Operator can show that they act only on requests that they have
believe are correct. This means that the Gateway must not pass on good reason to believe are correct. This means that the Gateway must
requests unless it is sure that they have not been corrupted in transit not pass on requests unless it is sure that they have not been
from the Requestor. corrupted in transit from the Requestor.
If a request can be shown to have come from a particular Requestor and If a request can be shown to have come from a particular Requestor
to have been acted on in good faith by the PINT service provider, then and to have been acted on in good faith by the PINT service provider,
responsibility for making requests may well fall to the Requestor rather then responsibility for making requests may well fall to the
than the Operator who executed these requests. Requestor rather than the Operator who executed these requests.
Finally, it may be important for the PINT service provider to be able to Finally, it may be important for the PINT service provider to be able
show that they act only on requests for which they have some degree of to show that they act only on requests for which they have some
assurance of origin. In many jurisdictions, it is a requirement on GSTN degree of assurance of origin. In many jurisdictions, it is a
Operators that they place calls only when they can, if required, requirement on GSTN Operators that they place calls only when they
identify the parties to the call (such as when required to carry out a can, if required, identify the parties to the call (such as when
Malicious Call Trace). It is at least likely that the provider of PINT required to carry out a Malicious Call Trace). It is at least likely
services will have a similar responsibility placed on them. that the provider of PINT services will have a similar responsibility
placed on them.
It follows that the PINT service provider may require that the identity It follows that the PINT service provider may require that the
of the Requestor be confirmed. If such confirmation is not available, identity of the Requestor be confirmed. If such confirmation is not
then they may be forced (or choose) not to provide service. This available, then they may be forced (or choose) not to provide
identification may require personal authentication of the Requesting service. This identification may require personal authentication of
User. the Requesting User.
5.1.2. Authority to make requests 5.1.2. Authority to make requests
Where GSTN resources are used to provide a PINT service, it is at least
possible that someone will have to pay for it. This person may not be
the Requestor, as, for example, in the case of existing GSTN
split-charging services like free phone in which the recipient of a call
rather than the originator is responsible for the call cost.
This is not, of course, the only possibility; for example, PINT service Where GSTN resources are used to provide a PINT service, it is at
may be provided on a subscription basis, and there are a number of other least possible that someone will have to pay for it. This person may
models. However, whichever model is chosen, there may be a requirement not be the Requestor, as, for example, in the case of existing GSTN
that the authority of a Requestor to make a PINT request is confirmed. split-charging services like free phone in which the recipient of a
call rather than the originator is responsible for the call cost.
If such confirmation is not available, then, again, the PINT Gateway and This is not, of course, the only possibility; for example, PINT
associated Executive System may choose not to provide service. service may be provided on a subscription basis, and there are a
number of other models. However, whichever model is chosen, there may
be a requirement that the authority of a Requestor to make a PINT
request is confirmed.
If such confirmation is not available, then, again, the PINT Gateway
and associated Executive System may choose not to provide service.
5.1.3. Privacy 5.1.3. Privacy
Even if the identity of the Requesting User and the Authority under
which they make their request is known, there remains the possibility
that the request is either corrupted, maliciously altered, or even
replaced whilst in transit between the Requestor and the PINT Gateway.
Similarly, information on the Authority under which a request is made Even if the identity of the Requesting User and the Authority under
may well be carried within that request. This can be sensitive which they make their request is known, there remains the possibility
information, as an eavesdropper might steal this and use it within their that the request is either corrupted, maliciously altered, or even
own requests. Such authority SHOULD be treated as if it were financial replaced whilst in transit between the Requestor and the PINT
information (such as a credit card number or PIN). Gateway.
The data authorizing a Requesting User to make a PINT request should be Similarly, information on the Authority under which a request is made
known only to them and the service provider. However, this information may well be carried within that request. This can be sensitive
may be in a form that does not match the schemes normally used within information, as an eavesdropper might steal this and use it within
the Internet. For example, X.509 certificates[14] are commonly used for their own requests. Such authority SHOULD be treated as if it were
secured transactions on the Internet both in the IP Security financial information (such as a credit card number or PIN).
Architecture[12] and in the TLS protocol[13], but the GSTN provider may
only store an account code and PIN (i.e. a fixed string of numbers).
A Requesting User has a reasonable expectation that their requests for The data authorizing a Requesting User to make a PINT request should
service are confidential. For some PINT services, no content is carried be known only to them and the service provider. However, this
over the Internet; however, the telephone or fax numbers of the parties information may be in a form that does not match the schemes normally
to a resulting service calls may be considered sensitive. As a result, used within the Internet. For example, X.509 certificates[14] are
it is likely that the Requestor (and their PINT service provider) will commonly used for secured transactions on the Internet both in the IP
require that any request that is sent across the Internet be protected Security Architecture[12] and in the TLS protocol[13], but the GSTN
against eavesdroppers; in short, the requests SHOULD to be encrypted. provider may only store an account code and PIN (i.e. a fixed string
of numbers).
A Requesting User has a reasonable expectation that their requests
for service are confidential. For some PINT services, no content is
carried over the Internet; however, the telephone or fax numbers of
the parties to a resulting service calls may be considered sensitive.
As a result, it is likely that the Requestor (and their PINT service
provider) will require that any request that is sent across the
Internet be protected against eavesdroppers; in short, the requests
SHOULD to be encrypted.
5.1.4. Privacy Implications of SUBSCRIBE/NOTIFY 5.1.4. Privacy Implications of SUBSCRIBE/NOTIFY
Some special considerations relate to monitoring sessions using the
SUBSCRIBE and NOTIFY messages. The SUBSCRIBE message that is used to
register an interest in the disposition of a PINT service transaction
uses the original Session Description carried in the related INVITE
message. This current specification does not restrict the source of such
a SUBSCRIBE message, so it is possible for an eavesdropper to capture an
unprotected session description and use this in a subsequent SUBSCRIBE
request. In this way it is possible to find out details on that
transaction that may well be considered sensitive.
The initial solution to this risk is to recommend that a session Some special considerations relate to monitoring sessions using the
description that may be used within a subsequent SUBSCRIBE message SUBSCRIBE and NOTIFY messages. The SUBSCRIBE message that is used to
SHOULD be protected. register an interest in the disposition of a PINT service transaction
uses the original Session Description carried in the related INVITE
message. This current specification does not restrict the source of
such a SUBSCRIBE message, so it is possible for an eavesdropper to
capture an unprotected session description and use this in a
subsequent SUBSCRIBE request. In this way it is possible to find out
details on that transaction that may well be considered sensitive.
However, there is a further risk; if the origin-field used is The initial solution to this risk is to recommend that a session
"guessable" then it might be possible for an attacker to reconstruct the description that may be used within a subsequent SUBSCRIBE message
session description and use this reconstruction within a SUBSCRIBE SHOULD be protected.
message.
SDP (see section 6 of [2], "o=" field) does not specify the mechansim However, there is a further risk; if the origin-field used is
used to generate the sess-id field, and suggests that a method based on "guessable" then it might be possible for an attacker to reconstruct
timestamps produced by Network Time Protocol [16] can be used. This is the session description and use this reconstruction within a
sufficient to guarantee uniqueness, but may allow the value to be SUBSCRIBE message.
guessed, particularly if other unprotected requests from the same
originator are available.
Thus, to ensure that the session identifier is not guessable the SDP (see section 6 of [2], "o=" field) does not specify the mechanism
techniques described in section 6.3 of [17] can be used when generating used to generate the sess-id field, and suggests that a method based
the origin-field for a session description to be used inside a PINT on timestamps produced by Network Time Protocol [16] can be used.
INVITE message. If all requests from (and responses to) a particular This is sufficient to guarantee uniqueness, but may allow the value
PINT requesting entity are protected, then this is not needed. Where to be guessed, particularly if other unprotected requests from the
such a situation is not assured, AND where session monitoring is same originator are available.
supported, then a method by which an origin-field within a session
description is not guessable SHOULD be used. Thus, to ensure that the session identifier is not guessable the
techniques described in section 6.3 of [17] can be used when
generating the origin-field for a session description to be used
inside a PINT INVITE message. If all requests from (and responses to)
a particular PINT requesting entity are protected, then this is not
needed. Where such a situation is not assured, AND where session
monitoring is supported, then a method by which an origin-field
within a session description is not guessable SHOULD be used.
5.2. Registration Procedures 5.2. Registration Procedures
Any number of PINT Gateways may register to provide the same service; Any number of PINT Gateways may register to provide the same service;
this is indicated by the Gateways specifying the same "userinfo" part in this is indicated by the Gateways specifying the same "userinfo" part
the To: header field of the REGISTER request. Whilst such ambiguity in the To: header field of the REGISTER request. Whilst such
would be unlikely to occur with the scenarios covered by "core" SIP, it ambiguity would be unlikely to occur with the scenarios covered by
is very likely for PINT; there could be any number of service providers "core" SIP, it is very likely for PINT; there could be any number of
all willing to support a "Request-To-Fax" service, for example. service providers all willing to support a "Request-To-Fax" service,
for example.
Unless a request specifies the Gateway name explicitly, an intervening Unless a request specifies the Gateway name explicitly, an
Proxy that acts on a registration database to which several Gateways intervening Proxy that acts on a registration database to which
have all registered is in a position to select from the registrands several Gateways have all registered is in a position to select from
using whatever algorithm it chooses; in principle, any Gateway that has the registrands using whatever algorithm it chooses; in principle,
registered as "R2F" would be appropriate. any Gateway that has registered as "R2F" would be appropriate.
However, this opens up an avenue for attack, and this is one in which a However, this opens up an avenue for attack, and this is one in which
"rogue" Gateway operator stands to make a significant gain. The standard a "rogue" Gateway operator stands to make a significant gain. The
SIP procedure for releasing a registration is to send a REGISTER request standard SIP procedure for releasing a registration is to send a
with a Contact field having a wildcard value and an expires parameter REGISTER request with a Contact field having a wildcard value and an
with a value of 0. It is important that a PINT Registrar uses expires parameter with a value of 0. It is important that a PINT
authentication of the Registrand, as otherwise one PINT service provider Registrar uses authentication of the Registrand, as otherwise one
would be able to "spoof" another and remove their registration. As this PINT service provider would be able to "spoof" another and remove
would stop the Proxy passing any requests to that provider, this would their registration. As this would stop the Proxy passing any requests
both increase requests being sent to the rogue and stop requests going to that provider, this would both increase requests being sent to the
to the victim. rogue and stop requests going to the victim.
Another variant on this attack would be to register a Gateway using a Another variant on this attack would be to register a Gateway using a
name that has been registered by another provider; thus a rogue Operator name that has been registered by another provider; thus a rogue
might register its Gateway as "R2C@pint.att.com", thereby hijacking Operator might register its Gateway as "R2C@pint.att.com", thereby
requests. hijacking requests.
The solution is the same; all registrations by PINT Gateways MUST be The solution is the same; all registrations by PINT Gateways MUST be
authenticated; this includes both new or apparent replacement authenticated; this includes both new or apparent replacement
registrations, and any cancellation of current registrations. This registrations, and any cancellation of current registrations. This
recommendation is also made in the SIP specification, but for the recommendation is also made in the SIP specification, but for the
correct operation of PINT, it is very important indeed. correct operation of PINT, it is very important indeed.
5.3. Security mechanisms and implications on PINT service 5.3. Security mechanisms and implications on PINT service
PINT is a set of extensions to SIP[1] and SDP[2], and will use the PINT is a set of extensions to SIP[1] and SDP[2], and will use the
security procedures described in SIP. There are several implications of security procedures described in SIP. There are several implications
this, and these are covered here. of this, and these are covered here.
For several of the PINT services, the To: header field of SIP is used to For several of the PINT services, the To: header field of SIP is used
identify one of the parties to the resulting service call. The PINT to identify one of the parties to the resulting service call. The
Request-To-Call service is an example. As mentioned in the SIP PINT Request-To-Call service is an example. As mentioned in the SIP
specification, this field is used to route SIP messages through an specification, this field is used to route SIP messages through an
infrastructure of Redirect and Proxy server between the corresponding infrastructure of Redirect and Proxy server between the corresponding
User Agent Servers, and so cannot be encrypted. This means that, User Agent Servers, and so cannot be encrypted. This means that,
although the majority of personal or sensitive data can be protected although the majority of personal or sensitive data can be protected
whilst in transit, the telephone (or fax) number of one of the parties whilst in transit, the telephone (or fax) number of one of the
to a PINT service call cannot, and will be "visible" to any parties to a PINT service call cannot, and will be "visible" to any
interception. For the PINT milestone services this may be acceptable, interception. For the PINT milestone services this may be acceptable,
since the caller named in the To: service is typically a "well known" since the caller named in the To: service is typically a "well known"
provider address, such as a Call Center. provider address, such as a Call Center.
Another aspect of this is that, even if the Requesting User does not Another aspect of this is that, even if the Requesting User does not
consider the telephone or fax numbers of the parties to a PINT service consider the telephone or fax numbers of the parties to a PINT
to be private, those parties might. Where PINT servers have reason to service to be private, those parties might. Where PINT servers have
believe this might be the case they SHOULD encrypt the request, even if reason to believe this might be the case they SHOULD encrypt the
the Requestor has not done so. This could happen, for example, if a request, even if the Requestor has not done so. This could happen,
Requesting User within a company placed a PINT request and this was for example, if a Requesting User within a company placed a PINT
carried via the company's Intranet to their Proxy/firewall and thence request and this was carried via the company's Intranet to their
over the Internet to a PINT Gateway at another location. Proxy/firewall and thence over the Internet to a PINT Gateway at
another location.
If a request carries data that can be reused by an eavesdropper either If a request carries data that can be reused by an eavesdropper
to "spoof" the Requestor or to obtain PINT service by inserting the either to "spoof" the Requestor or to obtain PINT service by
Requestor's authorization token into an eavesdropper's request, then inserting the Requestor's authorization token into an eavesdropper's
this data MUST be protected. This is particularly important if the request, then this data MUST be protected. This is particularly
authorization token consists of static text (such as an account code important if the authorization token consists of static text (such as
and/or PIN). an account code and/or PIN).
One approach is to encrypt the whole of the request, using the methods One approach is to encrypt the whole of the request, using the
described in the SIP specification. As an alternative, it may be methods described in the SIP specification. As an alternative, it may
acceptable for the authorization token to be held as an opaque reference be acceptable for the authorization token to be held as an opaque
(see section 3.4.2.3 and examples 4.11 and 4.12), using some proprietary reference (see section 3.4.2.3 and examples 4.11 and 4.12), using
scheme agreed between the Requestor and the PINT service provider, as some proprietary scheme agreed between the Requestor and the PINT
long as this is resistant to interception and re-use. Also, it may be service provider, as long as this is resistant to interception and
that the authorization token cannot be used outside of a request re-use. Also, it may be that the authorization token cannot be used
cryptographically signed by the Requestor; if so then this requirement outside of a request cryptographically signed by the Requestor; if so
can be relaxed, as in this case the token cannot be re-used by another. then this requirement can be relaxed, as in this case the token
However, unless both the Requestor and the Gateway are assured that this cannot be re-used by another. However, unless both the Requestor and
is the case, any authorization token MUST be treated as sensitive, and the Gateway are assured that this is the case, any authorization
so MUST be encrypted. token MUST be treated as sensitive, and so MUST be encrypted.
A PINT request may contain data within the SDP message body that can be A PINT request may contain data within the SDP message body that can
used more efficiently to route that request. For example, it may be that be used more efficiently to route that request. For example, it may
one Gateway and Executive System combination cannot handle a request be that one Gateway and Executive System combination cannot handle a
that specifies one of the parties as a pager, whilst another can. Both request that specifies one of the parties as a pager, whilst another
gateways may have registered with a PINT/SIP Registrar, and this can. Both gateways may have registered with a PINT/SIP Registrar, and
information may be available to intervening PINT/SIP Proxies. However, this information may be available to intervening PINT/SIP Proxies.
if the message body is encrypted, then the request cannot be decoded at However, if the message body is encrypted, then the request cannot be
the Proxy server, and so Gateway selection based on contained decoded at the Proxy server, and so Gateway selection based on
information cannot be made there. contained information cannot be made there.
The result is that the Proxy may deliver the request to a Gateway that The result is that the Proxy may deliver the request to a Gateway
cannot handle it; the implication is that a PINT/SIP Proxy SHOULD that cannot handle it; the implication is that a PINT/SIP Proxy
consider its choice for the appropriate Gateway subject to correction, SHOULD consider its choice for the appropriate Gateway subject to
and, on receiving a 501 or 415 rejection from the first gateway chosen, correction, and, on receiving a 501 or 415 rejection from the first
try another. In this way, the request will succeed if at all possible, gateway chosen, try another. In this way, the request will succeed if
even though it may be delayed (and tie up resources in the inappropriate at all possible, even though it may be delayed (and tie up resources
Gateways). in the inappropriate Gateways).
This opens up an interesting avenue for Denial Of Service; sending a This opens up an interesting avenue for Denial Of Service; sending a
valid request that appears to be suitable for a number of different valid request that appears to be suitable for a number of different
Gateways, and simply occupying those Gateways in decrypting a message Gateways, and simply occupying those Gateways in decrypting a message
requesting a service they cannot provide. As mentioned in section requesting a service they cannot provide. As mentioned in section
3.5.5.1, the choice of service name to be passed in the userinfo portion 3.5.5.1, the choice of service name to be passed in the userinfo
of the SIP Request-URI is flexible, and it is RECOMMENDED that names be portion of the SIP Request-URI is flexible, and it is RECOMMENDED
chosen that allow a Proxy to select an appropriate Gateway without that names be chosen that allow a Proxy to select an appropriate
having to examine the SDP body part. Thus, in the example given here, Gateway without having to examine the SDP body part. Thus, in the
the service might be called "Request-To-Page" or "R2P" rather than the example given here, the service might be called "Request-To-Page" or
more general use of "R2F", if there is a possibility of the SDP body "R2P" rather than the more general use of "R2F", if there is a
part being protected during transit. possibility of the SDP body part being protected during transit.
A variation on this attack is to provide a request that is syntactically A variation on this attack is to provide a request that is
invalid but that, due to the encryption, cannot be detected without syntactically invalid but that, due to the encryption, cannot be
expending resources in decoding it. The effects of this form of attack detected without expending resources in decoding it. The effects of
can be minimised in the same way as for any SIP Invitation; the Proxy this form of attack can be minimised in the same way as for any SIP
should detect the 400 rejection returned from the initial Gateway, and Invitation; the Proxy should detect the 400 rejection returned from
not pass the request onwards to another. the initial Gateway, and not pass the request onwards to another.
Finally, note that the Requesting User may not have a prior relationship Finally, note that the Requesting User may not have a prior
with a PINT Gateway, whilst still having a prior relationship with the relationship with a PINT Gateway, whilst still having a prior
Operator of the Executive System that fulfils their request. Thus there relationship with the Operator of the Executive System that fulfills
may be two levels of authentication and authorization; one carried out their request. Thus there may be two levels of authentication and
using the techniques described in the SIP specification (for use between authorization; one carried out using the techniques described in the
the Requestor and the Gateway), with another being used between the SIP specification (for use between the Requestor and the Gateway),
Requesting User or the Requestor and the Executive System. with another being used between the Requesting User or the Requestor
and the Executive System.
For example, the Requesting User may have an account with the PINT For example, the Requesting User may have an account with the PINT
service provider. That provider might require that requests include this service provider. That provider might require that requests include
identity before they will be convinced to provide service. In addition, this identity before they will be convinced to provide service. In
to counter attacks on the request whilst it is in transit across the addition, to counter attacks on the request whilst it is in transit
Internet, the Gateway may require a separate X.509-based certification across the Internet, the Gateway may require a separate X.509-based
of the request. These are two separate procedures, and data needed for certification of the request. These are two separate procedures, and
the former would normally be expected to be held in opaque references data needed for the former would normally be expected to be held in
inside the SDP body part of the request. opaque references inside the SDP body part of the request.
The detailed operation of this mechanism is, by definition, outside the The detailed operation of this mechanism is, by definition, outside
scope of an Internet Protocol, and so must be considered a private the scope of an Internet Protocol, and so must be considered a
matter. However, one approach to indicating to the Requestor that such private matter. However, one approach to indicating to the Requestor
"second level" authentication or authorization is required by their that such "second level" authentication or authorization is required
Service Provider would be to ask for this inside the textual description by their Service Provider would be to ask for this inside the textual
carried with a 401 response returned from the PINT Gateway. description carried with a 401 response returned from the PINT
Gateway.
5.4. Summary of Security Implications 5.4. Summary of Security Implications
From the above discussion, PINT always carries data items that are From the above discussion, PINT always carries data items that are
sensitive, and there may be financial considerations as well as the more sensitive, and there may be financial considerations as well as the
normal privacy concerns. As a result, the transactions MUST be protected more normal privacy concerns. As a result, the transactions MUST be
from interception, modification and replay in transit. protected from interception, modification and replay in transit.
PINT is based on SIP and SDP, and can use the security procedures PINT is based on SIP and SDP, and can use the security procedures
outlined in [1] (sections 13 and 15). However, in the case of PINT, the outlined in [1] (sections 13 and 15). However, in the case of PINT,
SIP recommendation that requests and responses MAY be protected is not the SIP recommendation that requests and responses MAY be protected
enough. PINT messages MUST be protected, so PINT Implementations MUST is not enough. PINT messages MUST be protected, so PINT
support SIP Security (as described in [1], sections 13 & 15), and be Implementations MUST support SIP Security (as described in [1],
capable of handling such received messages. sections 13 & 15), and be capable of handling such received messages.
In some configurations, PINT Clients, Servers, and Gateways can be sure In some configurations, PINT Clients, Servers, and Gateways can be
that they operate using the services of network level security [13], sure that they operate using the services of network level security
transport layer security [12], or physical security for all [13], transport layer security [12], or physical security for all
communications between them. In these cases messages MAY be exchanged communications between them. In these cases messages MAY be exchanged
without SIP security, since all traffic is protected already. Clients without SIP security, since all traffic is protected already. Clients
and servers SHOULD support manual configuration to use such lower layer and servers SHOULD support manual configuration to use such lower
security facilities. layer security facilities.
When using network layer security [13], the Security Policy Database When using network layer security [13], the Security Policy Database
MUST be configured to provide appropriate protection to PINT traffic. MUST be configured to provide appropriate protection to PINT traffic.
When using TLS, a port configured MUST NOT also be configured for When using TLS, a port configured MUST NOT also be configured for
non-TLS traffic. When TLS is used, basic authentication MUST be non-TLS traffic. When TLS is used, basic authentication MUST be
supported, and client-side certificates MAY be supported. supported, and client-side certificates MAY be supported.
Authentication of the Client making the request is required, however, so Authentication of the Client making the request is required, however,
if this is not provided by the underlying mechanism used, then it MUST so if this is not provided by the underlying mechanism used, then it
be included within the PINT messages using SIP authentication MUST be included within the PINT messages using SIP authentication
techniques. In contrast with SIP, PINT requests are often sent to techniques. In contrast with SIP, PINT requests are often sent to
parties with which a prior communications relationship exists (such as a parties with which a prior communications relationship exists (such
Telephone Carrier). In this case, there may be a shared secret between as a Telephone Carrier). In this case, there may be a shared secret
the client and the PINT Gateway. Such PINT systems MAY use between the client and the PINT Gateway. Such PINT systems MAY use
authentication based on shared secrets, with HTTP "basic authentication based on shared secrets, with HTTP "basic
authentication". When this is done, the message integrity and privacy authentication". When this is done, the message integrity and privacy
must be guaranteed by some lower layer mechanism. must be guaranteed by some lower layer mechanism.
There are implications on the operation of PINT here though. If a PINT There are implications on the operation of PINT here though. If a
proxy or redirect server is used, then it must be able to examine the PINT proxy or redirect server is used, then it must be able to
contents of the IP datagrams carried. It follows that an end-to-end examine the contents of the IP datagrams carried. It follows that an
approach using network-layer security between the PINT Client and a PINT end-to-end approach using network-layer security between the PINT
Gateway precludes the use of an intervening proxy; communication between Client and a PINT Gateway precludes the use of an intervening proxy;
the Client and Gateway is carried via a tunnel to which any intervening communication between the Client and Gateway is carried via a tunnel
entity cannot gain access, even if the IP datagrams are carried via this to which any intervening entity cannot gain access, even if the IP
node. Conversely, if a "hop-by-hop" approach is used, then any datagrams are carried via this node. Conversely, if a "hop-by-hop"
intervening PINT proxies (or redirect servers) are, by implication, approach is used, then any intervening PINT proxies (or redirect
trusted entities. servers) are, by implication, trusted entities.
However, if there is any doubt that there is an underlying network or However, if there is any doubt that there is an underlying network or
transport layer security association in place, then the players in a transport layer security association in place, then the players in a
PINT protocol exchange MUST use encryption and authentication techniques PINT protocol exchange MUST use encryption and authentication
within the protocol itself. The techniques described in section 15 of techniques within the protocol itself. The techniques described in
RFC2543 MUST be used, unless there is an alternative protection scheme section 15 of RFC2543 MUST be used, unless there is an alternative
that is agreed between the parties. In either case, the content of any protection scheme that is agreed between the parties. In either case,
message body (or bodies) carried within a PINT request or response MUST the content of any message body (or bodies) carried within a PINT
be protected; this has implications on the options for routing requests request or response MUST be protected; this has implications on the
via Proxies (see 5.3). options for routing requests via Proxies (see 5.3).
Using SIP techniques for protection, the Request-URI and To: fields Using SIP techniques for protection, the Request-URI and To: fields
headers within PINT requests cannot be protected. In the baseline PINT headers within PINT requests cannot be protected. In the baseline
services these fields may contain sensitive information. This is a PINT services these fields may contain sensitive information. This is
consideration, and if these data ARE considered sensitive, then this a consideration, and if these data ARE considered sensitive, then
will preclude the sole use of SIP techniques; in such a situation, this will preclude the sole use of SIP techniques; in such a
transport [12] or network layer [13] protection mechanisms MUST be used. situation, transport [12] or network layer [13] protection mechanisms
MUST be used.
As a final point, this choice will in turn have an influence on the As a final point, this choice will in turn have an influence on the
choice of transport layer protocol that can be used; if a TLS choice of transport layer protocol that can be used; if a TLS
association is available between two nodes, then TCP will have to be association is available between two nodes, then TCP will have to be
used. This is different from the default behaviour of SIP (try UDP, then used. This is different from the default behaviour of SIP (try UDP,
try TCP if that fails). then try TCP if that fails).
6. Deployment considerations and the Relationship PINT to I.N. 6. Deployment considerations and the Relationship PINT to I.N.
(Informative) (Informative)
6.1. Web Front End to PINT Infrastructure 6.1. Web Front End to PINT Infrastructure
It is possible that some other protocol may be used to communicate a It is possible that some other protocol may be used to communicate a
Requesting User's requirements. Due to the high numbers of available Web Requesting User's requirements. Due to the high numbers of available
Browsers and servers it seems likely that some PINT systems will use Web Browsers and servers it seems likely that some PINT systems will
HTML/HTTP as a "front end". In this scenario, HTTP will be used over a use HTML/HTTP as a "front end". In this scenario, HTTP will be used
connection from the Requesting User's Web Browser (WC) to an over a connection from the Requesting User's Web Browser (WC) to an
Intermediate Web Server (WS). This will be closely associated with a Intermediate Web Server (WS). This will be closely associated with a
PINT Client (using some unspecified mechanism to transfer the data from PINT Client (using some unspecified mechanism to transfer the data
the Web Server to the PINT Client). The PINT Client will represent the from the Web Server to the PINT Client). The PINT Client will
Requesting User to the PINT Gateway, and thus to the Executive System represent the Requesting User to the PINT Gateway, and thus to the
that carries out the required action. Executive System that carries out the required action.
[WC]------[WS] [WC]------[WS]
[PC] [PC]
\ \
\ \
[PG] [PG]
[XS] [XS]
Figure 2: Basic "Web-fronted" Configuration Figure 2: Basic "Web-fronted" Configuration
6.2. Redirects to Multiple Gateways 6.2. Redirects to Multiple Gateways
It is quite possible that a given PINT Gateway is associated with an It is quite possible that a given PINT Gateway is associated with an
Executive System (or systems) that can connect to the GSTN at different Executive System (or systems) that can connect to the GSTN at
places. Equally, if there is a chain of PINT Servers, then each of these different places. Equally, if there is a chain of PINT Servers, then
intermediate or proxy servers (PP) may be able to route PINT requests to each of these intermediate or proxy servers (PP) may be able to route
Executive Systems that connect at specific points to the GSTN. The PINT requests to Executive Systems that connect at specific points to
result of this is that there may be more than one PINT Gateway or the GSTN. The result of this is that there may be more than one PINT
Executive System that can deal with a given request. The mechanisms by Gateway or Executive System that can deal with a given request. The
which the choice on where to deliver a request are outside the scope of mechanisms by which the choice on where to deliver a request are
this document. outside the scope of this document.
[WC]------[WS] [WC]------[WS] [WC]------[WS] [WC]------[WS]
[PC] [PC] [PC] [PC]
\ \ \ \
\ \ \ \
[PG] [PP] [PG] [PP]
.........[XS]......... / \ .........[XS]......... / \
: : / \ : : / \
[PG] [PG] [PG] [PG]
[XS] [XS] [XS] [XS]
Figure 3: Multiple Access Configurations Figure 3: Multiple Access Configurations
However, there do seem to be two approaches. Either a Server that acts However, there do seem to be two approaches. Either a Server that
as a proxy or redirect will select the appropriate Gateway itself and acts as a proxy or redirect will select the appropriate Gateway
will cause the request to be sent on accordingly, or a list of possible itself and will cause the request to be sent on accordingly, or a
Locations will be returned to the Requesting User from which they can list of possible Locations will be returned to the Requesting User
select their choice. from which they can select their choice.
In SIP, the implication is that, if a proxy cannot resolve to a single In SIP, the implication is that, if a proxy cannot resolve to a
unique match for a request destination, then a response containing a single unique match for a request destination, then a response
list of the choices should be returned to the Requesting User for containing a list of the choices should be returned to the Requesting
selection. This is not too likely a scenario within the normal use of User for selection. This is not too likely a scenario within the
SIP. normal use of SIP.
However, within PINT, such ambiguity may be quite common; it implies However, within PINT, such ambiguity may be quite common; it implies
that there are a number of possible providers of a given service. that there are a number of possible providers of a given service.
6.3. Competing PINT Gateways REGISTERing to offer the same service 6.3. Competing PINT Gateways REGISTERing to offer the same service
With PINT, the registration is not for an individual but instead for a With PINT, the registration is not for an individual but instead for
service that can be handled by a service provider. Thus, one can a service that can be handled by a service provider. Thus, one can
envisage a registration by the PINT Server of the domain telcoA.com of envisage a registration by the PINT Server of the domain telcoA.com
its ability to support the service R2C as "R2C@telcoA.com", sent to an of its ability to support the service R2C as "R2C@telcoA.com", sent
intermediary server that acts as registrar for the "broker.telcos.com" to an intermediary server that acts as registrar for the
domain from "R2C@pint.telcoA.com" as follows: "broker.telcos.com" domain from "R2C@pint.telcoA.com" as follows:
REGISTER sip:registrar@broker.telcos.com SIP/2.0 REGISTER sip:registrar@broker.telcos.com SIP/2.0
To: sip:R2C@pint.telcoA.com To: sip:R2C@pint.telcoA.com
From: sip:R2C@pint.telcoA.com From: sip:R2C@pint.telcoA.com
... ...
This is the standard SIP registration service. This is the standard SIP registration service.
However, what happens if there are a number of different Service However, what happens if there are a number of different Service
Providers, all of whom support the "R2C" service? Suppose there is a Providers, all of whom support the "R2C" service? Suppose there is a
PINT system at domain "broker.com". PINT clients requesting a PINT system at domain "broker.com". PINT clients requesting a
Request-to-Call service from broker.com might be very willing to be Request-to-Call service from broker.com might be very willing to be
redirected or proxied to any one of the various service providers that redirected or proxied to any one of the various service providers
had previously registered with the registrar. PINT servers might also be that had previously registered with the registrar. PINT servers might
interested in providing service for requests that did not specify the also be interested in providing service for requests that did not
service provider explicitly, as well as those requests that were specify the service provider explicitly, as well as those requests
directed "at them". that were directed "at them".
To enable such service, PINT servers would REGISTER at the broker PINT To enable such service, PINT servers would REGISTER at the broker
server registrations of the form: PINT server registrations of the form:
REGISTER sip:registrar@broker.com SIP/2.0 REGISTER sip:registrar@broker.com SIP/2.0
To: sip:R2C@broker.com To: sip:R2C@broker.com
From: sip:R2C@pint.telcoA.com From: sip:R2C@pint.telcoA.com
When several such REGISTER messages appear at the registrar, each When several such REGISTER messages appear at the registrar, each
differing only in the URL in the From: line, the registrar has many differing only in the URL in the From: line, the registrar has many
possibilities, e.g.: possibilities, e.g.:
(i) it overwrites the prior registration for "R2C@broker.telcos.com" (i) it overwrites the prior registration for "R2C@broker.telcos.com"
when the next comes in; when the next comes in;
(ii) it rejects the subsequent registration for
"R2C@broker.telcos.com";
(iii) it maintains all such registrations.
In this last case, on receiving an Invitation for the "general" service, (ii) it rejects the subsequent registration for
either: "R2C@broker.telcos.com";
(iii.1) it passes on the invitation to all registered service
providers, returning a collated response with all
acceptances, using multiple Location: headers,
or
(iii.2) it silently selects one of the registrations (using, for
example, a "round robin" approach) and routes the Invitation
and response onwards without further comment.
As an alternative to all of the above approaches, it: (iii) it maintains all such registrations.
(iv) may choose to not allow registrations for the "general" service,
rejecting all such REGISTER requests.
The algorithm by which such a choice is made will be In this last case, on receiving an Invitation for the "general"
implementation-dependent, and is outside the scope of PINT. Where a service, either:
behaviour is to be defined by requesting users, then some sort of call
processing language might be used to allow those clients, as a
pre-service operation, to download the behaviour they expect to the
server making such decisions. This, however, is a topic for other
protocols, not for PINT.
6.4. Limitations on Available Information and Request Timing for (iii.1) it passes on the invitation to all registered service
SUBSCRIBE providers, returning a collated response with all
acceptances, using multiple Location: headers,
or
(iii.2) it silently selects one of the registrations (using, for
example, a "round robin" approach) and routes the Invitation
and response onwards without further comment.
A reference configuration for PINT is that service requests are sent, As an alternative to all of the above approaches, it:
via a PINT Gateway, to an Executive System that fulfils the Service
Control Function (SCF) of an Intelligent Network (see [11]). The success
or failure of the resulting service call may be information available to
the SCF and so may potentially be made available to the PINT Gateway. In
terms of historical record of whether or not a service succeeded, a
large SCF may be dealing with a million call attempts per hour. Given
that volume of service transactions, there are finite limits beyond
which it cannot store service disposition records; expecting to find out
if a Fax was sent last month from a busy SCF is unrealistic.
Other status changes, such as that on completion of a successful service (iv) may choose to not allow registrations for the "general" service,
call, require the SCF to arrange monitoring of the service call in a way rejecting all such REGISTER requests.
that the service may not do normally, for performance reasons. In most
implementations, it is difficult efficiently to interrupt a service to
change it once it has begun execution, so it may be necessary to have
two different services; one that sets GSTN resources to monitor service
call termination, and one that doesn't. It is unlikely to be possible to
decide that monitoring is required once the service has started.
These factors can have implications both on the information that is The algorithm by which such a choice is made will be implementation-
potentially available at the PINT Gateway, and when a request to dependent, and is outside the scope of PINT. Where a behaviour is to
register interest in the status of a PINT service can succeed. The be defined by requesting users, then some sort of call processing
alternative to using a general SCF is to provide a dedicated Service language might be used to allow those clients, as a pre-service
Node just for PINT services. As this node is involved in placing all operation, to download the behaviour they expect to the server making
service calls, it is in a position to collect the information needed. such decisions. This, however, is a topic for other protocols, not
However, it may well still not be able to respond successfully to a for PINT.
registration of interest in call state changes once a service logic
program instance is running.
Thus, although a Requesting User may register an interest in the status 6.4. Limitations on Available Information and Request Timing for
of a service request, the PINT Gateway may not be in a position to SUBSCRIBE
comply with that request. Although this does not affect the protocol
used between the Requestor and the PINT Gateway, it may influence the
response returned. To avoid the problem of changing service logic once
running, any registration of interest in status changes should be made
at or before the time at which the service request is made.
Conversely, if a historical request is made on the disposition of a A reference configuration for PINT is that service requests are sent,
service, this should be done within a short time after the service has via a PINT Gateway, to an Executive System that fulfills the Service
completed; the Executive System is unlikely to store the results of Control Function (SCF) of an Intelligent Network (see [11]). The
service requests for success or failure of the resulting service call may be information
available to the SCF and so may potentially be made available to the
PINT Gateway. In terms of historical record of whether or not a
service succeeded, a large SCF may be dealing with a million call
attempts per hour. Given that volume of service transactions, there
are finite limits beyond which it cannot store service disposition
records; expecting to find out if a Fax was sent last month from a
busy SCF is unrealistic.
long; these will have been processed as AMA (Automatic Message Other status changes, such as that on completion of a successful
Accounting) records quickly, after which the Executive System has no service call, require the SCF to arrange monitoring of the service
reason to keep them, and so they may be discarded. call in a way that the service may not do normally, for performance
reasons. In most implementations, it is difficult efficiently to
interrupt a service to change it once it has begun execution, so it
may be necessary to have two different services; one that sets GSTN
resources to monitor service call termination, and one that doesn't.
It is unlikely to be possible to decide that monitoring is required
once the service has started.
Where the PINT Gateway and the Executive System are intimately linked, These factors can have implications both on the information that is
the Gateway can respond to status subscription requests that occur while potentially available at the PINT Gateway, and when a request to
a service is running. It may accept these requests and simply not even register interest in the status of a PINT service can succeed. The
try to query the Executive System until it has information that a alternative to using a general SCF is to provide a dedicated Service
service has completed, merely returning the final status. Thus the PINT Node just for PINT services. As this node is involved in placing all
Requestor may be in what it believes is a monitoring state, whilst the service calls, it is in a position to collect the information needed.
PINT Gateway has not even informed the Executive System that a request However, it may well still not be able to respond successfully to a
has been made. This will increase the internal complexity of the PINT registration of interest in call state changes once a service logic
Gateway in that it will have a complex set of interlocking state program instance is running.
machines, but does mean that status registration and indication CAN be
provided in conjunction with an I.N. system. Thus, although a Requesting User may register an interest in the
status of a service request, the PINT Gateway may not be in a
position to comply with that request. Although this does not affect
the protocol used between the Requestor and the PINT Gateway, it may
influence the response returned. To avoid the problem of changing
service logic once running, any registration of interest in status
changes should be made at or before the time at which the service
request is made.
Conversely, if a historical request is made on the disposition of a
service, this should be done within a short time after the service
has completed; the Executive System is unlikely to store the results
of service requests for long; these will have been processed as AMA
(Automatic Message Accounting) records quickly, after which the
Executive System has no reason to keep them, and so they may be
discarded.
Where the PINT Gateway and the Executive System are intimately
linked, the Gateway can respond to status subscription requests that
occur while a service is running. It may accept these requests and
simply not even try to query the Executive System until it has
information that a service has completed, merely returning the final
status. Thus the PINT Requestor may be in what it believes is a
monitoring state, whilst the PINT Gateway has not even informed the
Executive System that a request has been made. This will increase the
internal complexity of the PINT Gateway in that it will have a
complex set of interlocking state machines, but does mean that status
registration and indication CAN be provided in conjunction with an
I.N. system.
6.5. Parameters needed for invoking traditional GSTN Services within 6.5. Parameters needed for invoking traditional GSTN Services within
PINT PINT
This section describes how parameters needed to specify certain This section describes how parameters needed to specify certain
traditional GSTN services can be carried within PINT requests. traditional GSTN services can be carried within PINT requests.
6.5.1. Service Identifier 6.5.1. Service Identifier
When a Requesting User asks for a service to be performed, he or she When a Requesting User asks for a service to be performed, he or she
will, of course, have to specify in some way which service. This can be will, of course, have to specify in some way which service. This can
done in the URLs within the To: header and the Request-URI (see section be done in the URLs within the To: header and the Request-URI (see
3.5.5.1). section 3.5.5.1).
6.5.2. A and B parties 6.5.2. A and B parties
With the Request-to-Call service, they will also need to specify the A With the Request-to-Call service, they will also need to specify the
and B parties they want to be engaged in the resulting service call. The A and B parties they want to be engaged in the resulting service
A party could identify, for example, the Call Center from which they call. The A party could identify, for example, the Call Center from
want a call back, whilst the B party is their telephone number (i.e. who which they want a call back, whilst the B party is their telephone
the Call Center agent is to call). number (i.e. who the Call Center agent is to call).
The Request-to-Fax and Request-to-Hear-Content services require the B The Request-to-Fax and Request-to-Hear-Content services require the B
party to be specified (respectively the telephone number of the party to be specified (respectively the telephone number of the
destination Fax machine or the telephone to which spoken content is to destination Fax machine or the telephone to which spoken content is
be delivered), but the A party is a Telephone Network based resource to be delivered), but the A party is a Telephone Network based
(either a Fax or speech transcoder/sender), and is implicit; the resource (either a Fax or speech transcoder/sender), and is implicit;
Requesting User does not (and cannot) specify it. the Requesting User does not (and cannot) specify it.
With the "Fax-Back" variant of the Request-to-Fax service, (i.e. where With the "Fax-Back" variant of the Request-to-Fax service, (i.e.
the content to be delivered resides on the GSTN) they will also have where the content to be delivered resides on the GSTN) they will also
specify two parties. As before, the B party is the telephone number of have specify two parties. As before, the B party is the telephone
the fax machine to which they want a fax to be sent. However, within number of the fax machine to which they want a fax to be sent.
this variant the A party identifies the "document context" for the However, within this variant the A party identifies the "document
GSTN-based document store from which a particular document is to be context" for the GSTN-based document store from which a particular
retrieved; the analogy here is to a GSTN user dialling a particular document is to be retrieved; the analogy here is to a GSTN user
telephone number and then entering the document number to be returned dialling a particular telephone number and then entering the document
using "touch tone" digits. The telephone number they dial is that of the number to be returned using "touch tone" digits. The telephone number
document store or A party, with the "touch tone" digits selecting the they dial is that of the document store or A party, with the "touch
document within that store. tone" digits selecting the document within that store.
6.5.3. Other Service Parameters 6.5.3. Other Service Parameters
In terms of the extra parameters to the request, the services again In terms of the extra parameters to the request, the services again
differ. The Request-to-Call service needs only the A and B parties. Also differ. The Request-to-Call service needs only the A and B parties.
it is convenient to assert that the resulting service call will carry Also it is convenient to assert that the resulting service call will
voice, as the Executive System within the destination GSTN may be able carry voice, as the Executive System within the destination GSTN may
to check that assertion against the A and B party numbers specified and be able to check that assertion against the A and B party numbers
may treat the call differently. specified and may treat the call differently.
With the Request-to-Fax and Request-to-Hear-Content services, the source With the Request-to-Fax and Request-to-Hear-Content services, the
information to be transcoded is held on the Internet. That means either source information to be transcoded is held on the Internet. That
that this information is carried along with the request itself, or that means either that this information is carried along with the request
a reference to the source of this information is given. itself, or that a reference to the source of this information is
given.
In addition, it is convenient to assert that the service call will carry In addition, it is convenient to assert that the service call will
fax or voice, and, where possible, to specify the format for the source carry fax or voice, and, where possible, to specify the format for
information. the source information.
The GSTN-based content or "Fax-Back" variant of the Request-to-Fax The GSTN-based content or "Fax-Back" variant of the Request-to-Fax
service needs to specify the Document Store number and the Fax machine service needs to specify the Document Store number and the Fax
number to which the information is to be delivered. It is convenient to machine number to which the information is to be delivered. It is
assert that the call will carry Fax data, as the destination Executive convenient to assert that the call will carry Fax data, as the
System may be able to check that assertion against the document store destination Executive System may be able to check that assertion
number and that of the destination Fax machine. against the document store number and that of the destination Fax
machine.
In addition, the document number may also need to be sent. This In addition, the document number may also need to be sent. This
parameter is an opaque reference that is carried through the Internet parameter is an opaque reference that is carried through the Internet
but has significance only within the GSTN. The document store number and but has significance only within the GSTN. The document store number
document number together uniquely specify the actual content to be and document number together uniquely specify the actual content to
faxed. be faxed.
6.5.4. Service Parameter Summary 6.5.4. Service Parameter Summary
The following table summarises the information needed in order to The following table summarises the information needed in order to
specify fully the intent of a GSTN service request. Note that it specify fully the intent of a GSTN service request. Note that it
excludes any other parameters (such as authentication or authorisation excludes any other parameters (such as authentication or
tokens, or Expires: or CallId: headers) that may be used in a request. authorisation tokens, or Expires: or CallId: headers) that may be
used in a request.
Service ServiceID AParty BParty CallFmt Source SourceFmt
R2C x x x voice - -
R2F x - x fax URI/IL ISF/ILSF
R2FB x x x fax OR -
R2HC x - x voice URI/IL ISF/ILSF
In this table, "x" means that the parameter is required, whilst "-" Service ServiceID AParty BParty CallFmt Source SourceFmt
means that the parameter is not required. ------- --------- ------ ------ ------- ------ -------
R2C x x x voice - -
R2F x - x fax URI/IL ISF/ILSF
R2FB x x x fax OR -
R2HC x - x voice URI/IL ISF/ILSF
In this table, "x" means that the parameter is required, whilst "-"
means that the parameter is not required.
The Services listed are Request-to-Call (R2C), Request-to-Fax (R2F), the The Services listed are Request-to-Call (R2C), Request-to-Fax (R2F),
GSTN-based content or "Fax-back" Variant of Request-to-Fax (R2FB), and the GSTN-based content or "Fax-back" Variant of Request-to-Fax
Request-to-Hear-Content (R2HC). (R2FB), and Request-to-Hear-Content (R2HC).
The Call Format parameter values "voice" or "fax" indicate the kind of The Call Format parameter values "voice" or "fax" indicate the kind
service call that results. of service call that results.
The Source Indicator "URI/IL" implies either that the information is The Source Indicator "URI/IL" implies that the information is either
either an Internet source reference (a Universal Resource Identifier, or an Internet source reference (a Universal Resource Identifier, or
URI) or is carried "in-line" with the message. The Source indicator "OR" URI) or is carried "in-line" with the message. The Source indicator
means that the value passed is an Opaque Reference that should be "OR" means that the value passed is an Opaque Reference that should
carried along with the rest of the message but is to be interpreted only be carried along with the rest of the message but is to be
within the destination (GSTN) context. As an alternative, it could be interpreted only within the destination (GSTN) context. As an
given as a "local" reference with the "file" style, or even using a alternative, it could be given as a "local" reference with the "file"
partial reference with the "http" style. However, the way in which such style, or even using a partial reference with the "http" style.
a reference is interpreted is a matter for the receiving PINT Server and However, the way in which such a reference is interpreted is a matter
Executive System; it remains, in effect, an opaque reference. for the receiving PINT Server and Executive System; it remains, in
effect, an opaque reference.
The Source Format value "ISF/ILSF" means that the format of the source The Source Format value "ISF/ILSF" means that the format of the
is specified either in terms of the URI or that it is carried "in-line". source is specified either in terms of the URI or that it is carried
Note that, for some data, the format either can be detected by "in-line". Note that, for some data, the format either can be
inspection or, if all else fails, can be assumed from the URI (for detected by inspection or, if all else fails, can be assumed from the
example, by assuming that the file extension part of a URL indicates the URI (for example, by assuming that the file extension part of a URL
data type). For an opaque reference, the Source Format is not available indicates the data type). For an opaque reference, the Source Format
on the Internet, and so is not given. is not available on the Internet, and so is not given.
6.6. Parameter Mapping to PINT Extensions 6.6. Parameter Mapping to PINT Extensions
This section describes the way in which the parameters needed to specify This section describes the way in which the parameters needed to
a GSTN service request fully might be carried within a "PINT extended" specify a GSTN service request fully might be carried within a "PINT
message. There are other choices, and these are not precluded. However, extended" message. There are other choices, and these are not
in order to ensure that the Requesting User receives the service that precluded. However, in order to ensure that the Requesting User
they expect, it is necessary to have some shared understanding of the receives the service that they expect, it is necessary to have some
parameters passed and the behaviour expected of the PINT Server and its shared understanding of the parameters passed and the behaviour
attendant Executive System. expected of the PINT Server and its attendant Executive System.
The Service Identifier can be sent as the userinfo element of the The Service Identifier can be sent as the userinfo element of the
Request-URI. Thus, the first line of a PINT Invitation would be of the Request-URI. Thus, the first line of a PINT Invitation would be of
form: the form:
INVITE <serviceID>@<pint-server>.<domain> SIP/2.0 INVITE <serviceID>@<pint-server>.<domain> SIP/2.0
The A Party for the Request-to-Call and "Fax-back" variant of The A Party for the Request-to-Call and "Fax-back" variant of
Request-to-Fax service can be held in the "To:" header field. In this Request-to-Fax service can be held in the "To:" header field. In this
case the "To:" header value will be different from the Request-URI. In case the "To:" header value will be different from the Request-URI.
the services where the A party is not specified, the "To:" field is free In the services where the A party is not specified, the "To:" field
to repeat the value held in the Request-URI. This is the case for is free to repeat the value held in the Request-URI. This is the case
Request-to-Fax and Request-to-Hear-Content services. for Request-to-Fax and Request-to-Hear-Content services.
The B party is needed in all these milestone services, and can be held The B party is needed in all these milestone services, and can be
in the enclosed SDP sub-part, as the value of the "c=" field. held in the enclosed SDP sub-part, as the value of the "c=" field.
The call format parameter can be held as part of the "m=" field value. The call format parameter can be held as part of the "m=" field
It maps to the "transport protocol" element as described in section value. It maps to the "transport protocol" element as described in
3.4.2 of this document. section 3.4.2 of this document.
The source format specifier is held in the "m=", as a type and either The source format specifier is held in the "m=", as a type and either
"-" or sub-type. The latter is normally required for all services except "-" or sub-type. The latter is normally required for all services
Request-to-Call or "Faxback", where the "-" form may be used. As shown except Request-to-Call or "Faxback", where the "-" form may be used.
earlier, the source format and source are not always required when As shown earlier, the source format and source are not always
generating requests for services. However, the inclusion in all requests required when generating requests for services. However, the
of a source format specifier can make parsing the request simpler and inclusion in all requests of a source format specifier can make
allows for other services to be specified in the future, and so values parsing the request simpler and allows for other services to be
are always given. The source format parameter is covered in section specified in the future, and so values are always given. The source
3.4.2 as the "media type" element. format parameter is covered in section 3.4.2 as the "media type"
element.
The source itself is identified by an "a=fmtp:" field value, where The source itself is identified by an "a=fmtp:" field value, where
needed. With the exception of the Request-to-Call service, all needed. With the exception of the Request-to-Call service, all
invitations will normally include such a field. From the perspective of invitations will normally include such a field. From the perspective
the SDP extensions, it can be considered as qualifying the media of the SDP extensions, it can be considered as qualifying the media
sub-type, as if to say, for example, "when I say jpeg, what I mean is sub-type, as if to say, for example, "when I say jpeg, what I mean is
the following". the following".
In summary, the parameters needed by the different services are carried In summary, the parameters needed by the different services are
in fields as shown in the following table: carried in fields as shown in the following table:
Service Svc Param PINT/SIP or SDP field used Example value Service Svc Param PINT/SIP or SDP field used Example value
------- --------- -------------------------- ------------- ------- --------- -------------------------- -------------
R2C R2C
ServiceID: <SIP Request-URI userinfo> R2C ServiceID: <SIP Request-URI userinfo> R2C
BParty: <SIP To: field> sip:123@p.com AParty: <SIP To: field> sip:123@p.com
AParty: <SDP c= field> TN RFC2543 4567 BParty: <SDP c= field> TN RFC2543 4567
CallFormat: <SDP transport protocol CallFormat: <SDP transport protocol
sub-field of m= field> voice sub-field of m= field> voice
SourceFmt: <SDP media type sub-field SourceFmt: <SDP media type sub-field
of m= field> audio of m= field> audio
(--- only "-" sub-type (--- only "-" sub-type
sub-field value used) --- sub-field value used) ---
Source: (--- No source specified) --- Source: (--- No source specified) ---
R2F R2F
ServiceID: <SIP Request-URI userinfo> R2F ServiceID: <SIP Request-URI userinfo> R2F
BParty: (--- SIP To: field not used) sip:R2F@pint.xxx.net AParty: (--- SIP To: field not used) sip:R2F@pint.xxx.net
AParty: <SDP c= field> TN RFCxxx +441213553 BParty: <SDP c= field> TN RFCxxx +441213553
CallFormat: <SDP transport protocol CallFormat: <SDP transport protocol
sub-field of m= field> fax sub-field of m= field> fax
SourceFmt: <SDP media type sub-field SourceFmt: <SDP media type sub-field
of m= field> image of m= field> image
<SDP media sub-type sub-field <SDP media sub-type sub-field
of m= field> jpeg of m= field> jpeg
Source: <SDP a=fmtp: field qualifying Source: <SDP a=fmtp: field qualifying
preceding m= field> a=fmtp:jpeg<uri-ref> preceding m= field> a=fmtp:jpeg<uri-ref>
R2FB R2FB
ServiceID: <SIP Request-URI userinfo> R2FB ServiceID: <SIP Request-URI userinfo> R2FB
BParty: <SIP To: field> sip:1-730-1234@p.com AParty: <SIP To: field> sip:1-730-1234@p.com
AParty: <SDP c= field> TN RFCxxx +441213553 BParty: <SDP c= field> TN RFCxxx +441213553
CallFormat: <SDP transport protocol CallFormat: <SDP transport protocol
sub-field of m= field> fax sub-field of m= field> fax
SourceFmt: <SDP media type sub-field SourceFmt: <SDP media type sub-field
of m= field> image of m= field> image
<SDP media sub-type sub-field <SDP media sub-type sub-field
of m= field> jpeg of m= field> jpeg
Source: <SDP a=fmtp: field qualifying Source: <SDP a=fmtp: field qualifying
preceding m= field> a=fmtp:jpeg opr:1234 preceding m= field> a=fmtp:jpeg opr:1234
R2HC R2HC
ServiceID: <SIP Request-URI userinfo> R2HC ServiceID: <SIP Request-URI userinfo> R2HC
BParty: (--- SIP To: field not used) sip:R2HC@pint.ita.il AParty: (--- SIP To: field not used) sip:R2HC@pint.ita.il
AParty: <SDP c= field> TN RFCxxx +441213554 BParty: <SDP c= field> TN RFCxxx +441213554
CallFormat: <SDP transport protocol CallFormat: <SDP transport protocol
sub-field of m= field> voice sub-field of m= field> voice
SourceFmt: <SDP media type sub-field SourceFmt: <SDP media type sub-field
of m= field> text of m= field> text
<SDP media sub-type sub-field <SDP media sub-type sub-field
of m= field> html of m= field> html
Source: <SDP a=fmtp: field qualifying Source: <SDP a=fmtp: field qualifying
preceding m= field> a=fmtp:html<uri-ref> preceding m= field> a=fmtp:html<uri-ref>
7. Open Issues and Draft State 7. References
7.1. Open Issues [1] Handley, M., Schooler, E., Schulzrinne, H. and J. Rosenberg,
"SIP: Session Initiation Protocol", RFC 2543, March 1999.
Thre are no current technical open issues. [2] Handley, M. and V. Jacobsen, "SDP: Session Description
Protocol", RFC 2327, April 1998.
7.2. Draft State [3] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bodies",
RFC 2045, November 1996.
This draft reflects all changes resulting from the WG "last call" phase. [4] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046, November
1996.
8. References [5] The Unicode Consortium, "The Unicode Standard -- Version 2.0",
Addison-Wesley, 1996.
[1] M. Handley, E. Schooler, H. Schulzrinne, & J. Rosenberg, [6] ITU-T Study Group 2, "E.164 - The International Public Network
"SIP: Session Initiation Protocol", RFC2543, Numbering Plan", ITU-T, June 1997.
Internet Engineering Task Force, March 1999.
[2] M. Handley & V. Jacobsen,
"SDP: Session Description Protocol", RFC2327,
Internet Engineering Task Force, April 1998.
[3] N. Freed & N. Borenstein,
"Multipurpose Internet Mail Extensions (MIME)
Part One: Format of Internet Message Bodies",
RFC2045, November 1996.
[4] N. Freed & N. Borenstein,
"Multipurpose Internet Mail Extensions (MIME)
Part Two: Media Types",
RFC2046, November 1996.
[5] The Unicode Consortium,
"The Unicode Standard -- Version 2.0",
Addison-Wesley, 1996.
[6] ITU-T Study Group 2,
"E.164 - The International Public Network Numbering Plan",
ITU-T, June 1997.
[7] H. Lu et al,
"Toward the PSTN/Internet Inter-Networking--Pre-PINT
Implementations", Informational RFC2458,
Internet Engineering Task Force, Nov 1998.
[8] ITU-T Study Group XI,
"Q.763 - Formats and Codes for the ISDN User Part of SS No7"
ITU-T, August 1994.
[9] T. Berners-Lee, R. Fielding, & L. Masinter, [7] Lu, H., Krishnaswamy, M., Conroy, L., Bellovin, S., Burg, F.,
"Uniform Resource Identifiers (URI): Generic Syntax", RFC2396, DeSimone, A., Tewani, K., Davidson, P., Schulzrinne, H. and K.
Internet Engineering Task Force, August 1998. Vishwanathan "Toward the PSTN/Internet Inter-Networking--Pre-
[10] D. Crocker, PINT Implementations", RFC 2458, November 1998.
"Standard for the format of ARPA Internet text messages",RFC822,
Internet Engineering Task Force, August 1982.
[11] ITU-T Study Group XI,
"Q.1204 - IN Distributed Functional Plane Architecture",
ITU-T, February 1994.
[12] T. Dierks & C. Allen,
"The TLS Protocol Version 1.0", RFC2246,
Internet Engineering Task Force, January 1999.
[13] S. Kent, R. Atkinson,
"Security Architecture for the Internet Protocol", RFC2401,
Internet Engineering Task Force, November 1998.
[14] R. Housley, W. Ford, W. Polk & D. Solo,
"Internet X.509 Public Key Infrastructure Certificate and CRL
Profile", RFC2459,
Internet Engineering Task Force, January 1999.
[15] D. Crocker & P. Overall,
"Augmented BNF for Syntax Specifications: ABNF", RFC2234,
Internet Engineering Task Force, November 1997.
[16] D. Mills, "Network Time Protocol (version 3) specification and
implementation", RFC1305, Internet Engineering Task Force,
March 1992.
[17] D. Eastlake, S. Crocker & J.Schiller,
"Randomness Recommendations for Security", Informational RFC 1305,
Internet Engineering Task Force, March 1992.
[18] P. Mockapetris,
"Domain Names - Implementation and Specification" RFC 1035,
Inernet Engineering Task Force November 1987.
[19] E. Levinson,
"The MIME Multipart/Related Content-type" RFC 2387,
Inernet Engineering Task Force August 1998.
9. Acknowledgements [8] ITU-T Study Group XI, "Q.763 - Formats and Codes for the ISDN
User Part of SS No7" ITU-T, August 1994.
The authors wish to thank the members of the PINT working group for [9] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
comments that were helpful to the preparation of this specification. Ian Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
Elz's comments were extremely useful to our understanding of internal
PSTN operations. The SUBSCRIBE and NOTIFY requests were first suggested [10] Crocker, D., "Standard for the format of ARPA Internet text
by Henning Schulzrinne and Jonathan Rosenberg. The suggestion to use messages", STD 11, RFC 822, August 1982.
an audio port of 0 to express that the phone is "on hold" (i.e. not
receiving voice) is due to Ray Zibman. Finally, thanks to Bernie [11] ITU-T Study Group XI, "Q.1204 - IN Distributed Functional Plane
Hoeneisen for his close proofreading. Architecture", ITU-T, February 1994.
[12] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC
2246, January 1999.
[13] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[14] Housley, R., Ford, W., Polk W. and D. Solo, "Internet X.509
Public Key Infrastructure Certificate and CRL Profile", RFC
2459, January 1999.
[15] Crocker, D. and P. Overall, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[16] Mills, D., "Network Time Protocol (version 3) specification and
implementation", RFC 1305, March 1992.
[17] Eastlake, D., Crocker, S. and J.Schiller, "Randomness
Recommendations for Security", RFC 1750, December 1994.
[18] Mockapetris, P., "Domain Names - Implementation and
Specification", STD 13, RFC 1035, November 1987.
[19] Levinson, E., "The MIME Multipart/Related Content-type" RFC
2387, August 1998.
8. Acknowledgements
The authors wish to thank the members of the PINT working group for
comments that were helpful to the preparation of this specification.
Ian Elz's comments were extremely useful to our understanding of
internal PSTN operations. The SUBSCRIBE and NOTIFY requests were
first suggested by Henning Schulzrinne and Jonathan Rosenberg. The
suggestion to use an audio port of 0 to express that the phone is "on
hold" (i.e. not receiving voice) is due to Ray Zibman. Finally,
thanks to Bernie Hoeneisen for his close proofreading.
Appendix A: Collected ABNF for PINT Extensions Appendix A: Collected ABNF for PINT Extensions
;; --(ABNF is specified in RFC 2234 [15]) ;; --(ABNF is specified in RFC 2234 [15])
;; --Variations on SDP definitions ;; --Variations on SDP definitions
connection-field = ["c=" nettype space addrtype space connection-field = ["c=" nettype space addrtype space
connection-address CRLF] connection-address CRLF]
; -- this is the original definition from SDP, included for completeness ; -- this is the original definition from SDP, included for completeness
; -- the following are PINT interpretations and modifications ; -- the following are PINT interpretations and modifications
nettype = ("IN"/"TN") nettype = ("IN"/"TN")
skipping to change at page 58, line 16 skipping to change at page 66, line 21
; -- 0 retains usual sdp meaning of "temporarily no media" ; -- 0 retains usual sdp meaning of "temporarily no media"
; -- (i.e. "line is on hold") ; -- (i.e. "line is on hold")
; -- (1 means there is media) ; -- (1 means there is media)
proto = (INProto/TNProto) proto = (INProto/TNProto)
; -- redefined as a superset of the original SDP definition ; -- redefined as a superset of the original SDP definition
INProto = 1* (<alpha-numeric>) INProto = 1* (<alpha-numeric>)
; -- this is the "classic" SDP protocol, defined if nettype == "IN" ; -- this is the "classic" SDP protocol, defined if nettype == "IN"
; -- alpha-numeric is as defined in SDP ; -- alpha-numeric is as defined in SDP
..--
TNProto = ("voice"/"fax"/"pager") TNProto = ("voice"/"fax"/"pager")
; -- this is the PINT protocol, defined if nettype == "TN" ; -- this is the PINT protocol, defined if nettype == "TN"
fmt = (<subtype> / "-") fmt = (<subtype> / "-")
; -- NOTE redefined as a subset of the original SDP definition ; -- NOTE redefined as a subset of the original SDP definition
; -- subtype as defined in RFC2046, or "-". MUST be a subtype of type ; -- subtype as defined in RFC2046, or "-". MUST be a subtype of type
held held
; -- in associated media sub-field or the special value "-". ; -- in associated media sub-field or the special value "-".
attribute-fields = *("a=" attribute-list <CRLF>) attribute-fields = *("a=" attribute-list <CRLF>)
skipping to change at page 59, line 25 skipping to change at page 67, line 32
network-prefix = intl-network-prefix / local-network-prefix network-prefix = intl-network-prefix / local-network-prefix
intl-network-prefix = "+" 1*<DIGIT> intl-network-prefix = "+" 1*<DIGIT>
local-network-prefix = 1*<DIGIT> local-network-prefix = 1*<DIGIT>
private-prefix = 1*excldigandplus 0*<uric> private-prefix = 1*excldigandplus 0*<uric>
excldigandplus = (0x21-0x2d,0x2f,0x40-0x7d)) excldigandplus = (0x21-0x2d,0x2f,0x40-0x7d))
..--
tsp-attribute = tsp-tag "=" provider-domainname tsp-attribute = tsp-tag "=" provider-domainname
tsp-tag = "tsp" tsp-tag = "tsp"
provider-domainname = <domain> provider-domainname = <domain>
; -- domain is defined in RFC1035 ; -- domain is defined in RFC1035
; -- NOTE the following is redefined relative to the normal use in SDP ; -- NOTE the following is redefined relative to the normal use in SDP
pint-fmtp-attribute = "fmtp:" <subtype> <space> resolution pint-fmtp-attribute = "fmtp:" <subtype> <space> resolution
*(<space> resolution) *(<space> resolution)
skipping to change at page 61, line 7 skipping to change at page 69, line 20
Require-header = "require:" 1(required-extensions) Require-header = "require:" 1(required-extensions)
*("," required-extensions) *("," required-extensions)
; -- NOTE this is redefined as a subset of the SIP definition ; -- NOTE this is redefined as a subset of the SIP definition
; -- (from RFC2543/section 6.30) ; -- (from RFC2543/section 6.30)
required-extensions = ("org.ietf.sip.subscribe" / required-extensions = ("org.ietf.sip.subscribe" /
"org.ietf.sdp.require") "org.ietf.sdp.require")
Appendix B: IANA Considerations Appendix B: IANA Considerations
There are three kinds of identifier used in PINT extensions that SHOULD There are three kinds of identifier used in PINT extensions that
be registered with IANA, if a new value is specified. These are: SHOULD be registered with IANA, if a new value is specified. These
* Media Format sub-types, as described in section 3.4.2 of this are:
document.
* Private Attributes as mentioned in section 3.4.3
* Private Phone Context values, as described in section 3.4.3.1.
It should be noted that private Address Types (in section 3.4.1) have * Media Format sub-types, as described in section 3.4.2 of this
been explicitly excluded from this process, as they must be in the form document.
of an X-Token. * Private Attributes as mentioned in section 3.4.3
* Private Phone Context values, as described in section 3.4.3.1.
It should be noted that private Address Types (in section 3.4.1) have
been explicitly excluded from this process, as they must be in the
form of an X-Token.
B.1. Media Format Sub-types B.1. Media Format Sub-types
Taking these in turn, the media format sub-types are used within the
PINT extensions to SDP to specify the attribute line that holds the data
source definitions. In normal use, the values in this field are
sub-types of MIME discrete types[4]. If a value other than an
IANA-registered sub-type is to be used, then it should either be an
X-Token (i.e. start with "X-") or it should be registered with IANA. if
the intention is to describe a new MIME sub-type, then the procedures
specified in RFC 2048 should be used. It is ASSUMED that any new MIME
sub-type would follow the syntactic rules for interpretation of
associated PINT fmtp lines defined in this document.
Note that, in keeping with the SDP description, such registrations Taking these in turn, the media format sub-types are used within the
SHOULD include the "proto" field values within which they are defined; PINT extensions to SDP to specify the attribute line that holds the
however, it is appropriate to specify only that they can be used with data source definitions. In normal use, the values in this field are
"all values of TNProto". sub-types of MIME discrete types[4]. If a value other than an IANA-
registered sub-type is to be used, then it should either be an X-
Token (i.e. start with "X-") or it should be registered with IANA. if
the intention is to describe a new MIME sub-type, then the procedures
specified in RFC 2048 should be used. It is ASSUMED that any new MIME
sub-type would follow the syntactic rules for interpretation of
associated PINT fmtp lines defined in this document.
Conversely, if the intent is to define a new way of including data Note that, in keeping with the SDP description, such registrations
source definitions within PINT, then it will be necessary to specify, in SHOULD include the "proto" field values within which they are
the documentation supporting any such new "PINT Media Format Sub-type" defined; however, it is appropriate to specify only that they can be
registration, the syntax of the associated "fmtp" attribute line, as the used with "all values of TNProto".
identifier serves to indicate the interpretation that should be made of
format specific attribute lines "tagged" with with such a sub-type.
If the fmtp interpretation follows the PINT default, then it is adequate Conversely, if the intent is to define a new way of including data
to mention this in the defining document rather than repeating the source definitions within PINT, then it will be necessary to specify,
syntax definition given here (although, in this case, it is unclear why in the documentation supporting any such new "PINT Media Format Sub-
such a new registration would be required). As before, the Media Format type" registration, the syntax of the associated "fmtp" attribute
sub-type SHOULD specify the values of "proto" field within which it is line, as the identifier serves to indicate the interpretation that
defined, but this can be "all values of TNProto". should be made of format specific attribute lines "tagged" with such
a sub-type.
If the fmtp interpretation follows the PINT default, then it is
adequate to mention this in the defining document rather than
repeating the syntax definition given here (although, in this case,
it is unclear why such a new registration would be required). As
before, the Media Format sub-type SHOULD specify the values of
"proto" field within which it is defined, but this can be "all values
of TNProto".
B.2. Private Attributes B.2. Private Attributes
Any proprietary attribute lines that are added may be registered with
IANA using the procedures mentioned in [2]; the mechanism is the same as Any proprietary attribute lines that are added may be registered with
that used in SDP. If the attribute is defined for use only within PINT, IANA using the procedures mentioned in [2]; the mechanism is the same
then it may be approapriate to mention this in the supporting as that used in SDP. If the attribute is defined for use only within
documentation. Note that, in the PINT 1.0 specification covered here, PINT, then it may be appropriate to mention this in the supporting
there is no mechanism to add such freshly registered attribute lines to documentation. Note that, in the PINT 1.0 specification covered here,
a "require:" clause. there is no mechanism to add such freshly registered attribute lines
to a "require:" clause.
B.3. Private phone-contexts B.3. Private phone-contexts
Within the session description used for PINT requests, a phone-context
attribute may be used to specify the prefix or context within which an
associated telephone-number (in a connextion line) should be
interpreted.
For "public" phone contexts the prefix to be used MUST start with either Within the session description used for PINT requests, a phone-
a DIGIT or a "+". Private phone contexts may be registered with IANA context attribute may be used to specify the prefix or context within
that do NOT start with either of these characters. Such a prefix may be which an associated telephone-number (in a connection line) should be
useful to identify a private network, potentially with an associated interpreted.
numeric ID (see example 4 in section 3.4.3.1). In the example, the
prefix acts as the context for X-acme.com's private network numbering
plan.
It is recommended that any private context to be registered have the For "public" phone contexts the prefix to be used MUST start with
general form of a token including a domain name, optionally followed by either a DIGIT or a "+". Private phone contexts may be registered
a digit string or other token. The appropriate form of the initial token with IANA that do NOT start with either of these characters. Such a
name space will be similar to that used for private or vendor prefix may be useful to identify a private network, potentially with
registrations for sub-types (e.g. vnd.acme.com). However, note that the an associated numeric ID (see example 4 in section 3.4.3.1). In the
registration will be used to specify a customer's private network example, the prefix acts as the context for X-acme.com's private
numbering plan format rather than being used generally for all of their network numbering plan.
equipment vendor's customer's; thus, fbi.gov would be appropriate, but
lucent.com would not (unless the private network were to be that used by
Lucent internally).
In addition, the supporting documentation MUST either declare that there It is recommended that any private context to be registered have the
is no associated token, or define the syntax by which that token can be general form of a token including a domain name, optionally followed
parsed (e.g. vnd.fbi.gov <space> 1*DIGIT). Note that the registration by a digit string or other token. The appropriate form of the initial
describes a format, not a value range; it is sufficient that the private token name space will be similar to that used for private or vendor
context can be parsed, without the value being interpreted. registrations for sub-types (e.g. vnd.acme.com). However, note that
the registration will be used to specify a customer's private network
numbering plan format rather than being used generally for all of
their equipment vendor's customer's; thus, fbi.gov would be
appropriate, but lucent.com would not (unless the private network
were to be that used by Lucent internally).
In detail, the registration request SHOULD include: In addition, the supporting documentation MUST either declare that
* Kind of registration (i.e. private phone-context attribute to be there is no associated token, or define the syntax by which that
used within the service description of PINT service requests) token can be parsed (e.g. vnd.fbi.gov <space> 1*DIGIT). Note that the
* Contact details for the person responsible for the registration registration describes a format, not a value range; it is sufficient
request (name, organisation, e-mail address, public telephone that the private context can be parsed, without the value being
number) interpreted.
* Private Prefix initial token name (e.g. vnd.fbi.gov)
* syntax for private context (e.g. "vnd.fbi.gov" <space> 1*DIGIT, or
"vnd.gtn.gov.uk")
* Description of use (e.g. "This phone context declares an associated
telephone number to be within the 'government telecommunications
network'; the number is in an internal or private number plan form)
* Network Type and Address Type with which this private context is
associated; If the "normal" telephone types (as specified in this
document) are used, then the values would be shown as:
"nettype=TN" , addrtype="RFC2543Addr". If, however, this context
were to be used with another address type, then a reference to that
address type name and the syntax of that address value would be
required.
In short, this context is the telephone equivalent of a "Net 10" address In detail, the registration request SHOULD include:
space behind a NAT, and the initial name (and contact information) shows
the context within which that address is valid. It also specifies the
format for the network and address types (and address value syntax) with
which this context is associated.
Of course, IANA may refer the requested registration to the IESG or an * Kind of registration (i.e. private phone-context attribute to be
appropriate IETF working group for review, and may require revisions to used within the service description of PINT service requests)
be made before the registration is accepted. * Contact details for the person responsible for the registration
request (name, organisation, e-mail address, public telephone
number)
* Private Prefix initial token name (e.g. vnd.fbi.gov)
* syntax for private context (e.g. "vnd.fbi.gov" <space> 1*DIGIT, or
"vnd.gtn.gov.uk")
* Description of use (e.g. "This phone context declares an
associated telephone number to be within the 'government
telecommunications network'; the number is in an internal or
private number plan form)
* Network Type and Address Type with which this private context is
associated; If the "normal" telephone types (as specified in this
document) are used, then the values would be shown as:
"nettype=TN" , addrtype="RFC2543Addr". If, however, this context
were to be used with another address type, then a reference to
that address type name and the syntax of that address value would
be required.
Appendix C: Author's Addresses In short, this context is the telephone equivalent of a "Net 10"
address space behind a NAT, and the initial name (and contact
information) shows the context within which that address is valid. It
also specifies the format for the network and address types (and
address value syntax) with which this context is associated.
Scott Petrack Of course, IANA may refer the requested registration to the IESG or
MetaTel, Inc. an appropriate IETF working group for review, and may require
35 Rumford Avd. revisions to be made before the registration is accepted.
Waltham, MA 02453
scott.petrack@metatel.com
+1 (781)-891-9000
Lawrence Conroy Authors' Addresses
Siemens Roke Manor Research
Roke Manor
Old Salisbury Lane
Romsey, Hampshire
U.K. SO51 0ZN
lwc@roke.co.uk
+44 (1794) 833666
Petrack & Conroy [Page 63] Scott Petrack
MetaTel, Inc.
45 Rumford Ave.
Waltham MA 02453-3844
Phone: +1 (781)-891-9000
EMail: scott.petrack@metatel.com
Lawrence Conroy
Siemens Roke Manor Research
Roke Manor
Old Salisbury Lane
Romsey, Hampshire
U.K. SO51 0ZN
Phone: +44 (1794) 833666
EMail: lwc@roke.co.uk
Full Copyright Statement
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Acknowledgement
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